UV curable elastomer composition

ABSTRACT

Ethylene copolymer elastomer compositions, acrylate rubber compositions, nitrile rubber compositions, fluoroelastomer compositions, and chlorinated olefin elastomer compositions are provided which are curable by exposure to UV radiation. The compositions are particularly suited for production of elastomeric seals using hot melt equipment and a gasketing in place technique.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part of co-pending application Ser. No.09/234,014 filed Jan. 19, 1999 which claims the benefit of U.S.Provisional Application 60/072,109 filed Jan. 21, 1998.

FIELD OF THE INVENTION

[0002] This invention relates to elastomeric compositions that arecurable by exposure to ultraviolet (UV) radiation. In addition, thisinvention relates to a process for curing elastomeric seals rapidly,wherein the seals are formed by applying an uncured polymer compositiondirectly onto a sealing element or a surface to be sealed. Thisinvention further relates to cured articles produced by the process ofthe invention.

BACKGROUND OF THE INVENTION

[0003] Elastorneric compositions require a vulcanization, i.e. curing,step in order to develop the crosslinked network structure which confersoptimum rubbery properties to such compositions. Typically, the curingprocesses are based on compression molding or transfer moldingtechniques wherein an elastomer, fully compounded with curing agent andother additives, is introduced into a mold that is then heated underpressure. The elevated temperatures used during the molding processcause chemical reaction of the elastomer and curative, thereby producinga crosslinked product.

[0004] The particular raw (i.e. uncured) elastomer used to manufacture asynthetic rubber article will be selected with reference to the specificend use application and environment under which the finished articlemust function. For example, one will select different elastomers fromamong ethylene alkyl acrylate copolymer rubbers, ethylene alpha-olefincopolymer elastomers, fluoroelastomers and chlorinated elastomersdepending upon whether the finished article will be exposed to oils,water, fuels, acids or bases. One will also consider the temperaturerange to which the article will be subjected and special requirementssuch as flame resistance. In addition, consideration will be given tothe cure characteristics of the polymer and the ease with whichdefect-free parts can be produced.

[0005] The majority of elastomeric seals manufactured on a commercialscale are crosslinked at high temperature in molding processes.Generally, elastomeric seals and gaskets thus produced are manuallyfitted onto an article to be sealed. Alternatively, adhesives aresometimes utilized to attach the cured sealing member to an article.Such attachment techniques are not completely satisfactory in all cases.In particular, manual methods are time consuming and adhesives canaffect the physical properties of the seal.

[0006] Elastomeric gaskets are often utilized as sealing members forgrooved parts, such as rocker covers and air intake manifolds, that areused in automobile engines. Such gaskets must be resistant to theeffects of heat and oil. Traditionally, cured, oil-resistant elastomercompositions, such as ethylene alkyl acrylate copolymer rubbers, havebeen manually introduced into the groove of a metal part. Manyautomotive components are now formed from high performance thermoplasticmaterials, rather than from metal. Manual fitting of elastomeric sealsonto these components is time-consuming, but curing the seal in place isimpractical because either the cure temperature or, in some cases, thepost cure temperature, is usually high enough to cause deformation ofthe thermoplastic. Yet, if the cure temperature is lowered, cure rate istoo slow to be practical. Oil or fuel resistant elastomeric compositionsthat could be readily applied to an article or groove in their uncuredstate and that are adapted to low temperature curing techniques wouldtherefore be especially useful in manufacture of thermoplastic articleshaving attached sealing members for automotive or industrial uses.

[0007] Low temperature curing processes that are initiated by highenergy radiation, such as electron beam or γ-radiation, are known foruse with almost any elastomer, including ethylene acrylate copolymerelastomers. For example, electron beam crosslinking of wire and cableinsulation compositions, including elastomeric compositions, isdisclosed in E. Brandt and A. Berejka, Electron Beam Crosslinking ofWire and Cable Insulation, Rubber World, 49, November 1978. Eldred, inU.S. Pat. No. 3,950,238, discloses the use of electron beam radiation tocure acrylonitrile butadiene polymers and Clarke, in U.S. Pat. No.4,275,180, discloses the use of electron beam radiation cure of a blendof an ethylene acrylate copolymer rubber and a thermoplastic polymer,e.g. for cable jacketing. Electron beam cures have the disadvantage ofrequiring quite complex and expensive equipment for generating highenergy particles. It would therefore be advantageous to have available alow temperature curing process that did not rely on the use of electronbeam radiation. Low temperature UV cures of a variety of polymers,including ethylene acrylate polymers, are disclosed in U.S. Pat. No.4,863,536. However, the disclosed process involves dissolution of theparticular polymer in an acrylate monomer and is not suitable forpreparation of general rubber goods, such as gaskets and seals.

[0008] In addition to having available an effective low temperature cureprocess for ethylene acrylate copolymer elastomers, it would also beadvantageous to have available similar curing techniques for use withother elastomers as well. As is the case with ethylene acrylatecopolymers, typical curing processes for fluoroelastomers are based onhigh temperature compression molding or transfer molding techniques.Products made using such processes include seals, gaskets, tubing, andother general rubber goods. In addition, textile composites coated withfluoroelastomers are available commercially and are generally subjectedto a baking process during fabrication, for example as disclosed in U.S.Pat. No. 4,770,927 to Effenberger et al.

[0009] Low temperature radiation curing processes for fluoroelastomersare known in the prior art. For example, a stain-resistant protectivefluoroelastomer coating composition for flooring that is curable usingUV radiation is disclosed in European Patent Application 570254. UV cureof epoxy-containing fluorinated copolymers is described in JapaneseKokai Patent Application 5-302058. In addition, UV or electron beamcures of certain fluoroelastomer compositions that are normally curedwith a polyol or polyamine crosslinking agent are disclosed in GermanPatent 19642029 and in Japanese Kokai Patent Application 61-031411.Blends of fluoroplastics and ethylene vinyl acetate copolymers orethylene acrylic acid ester copolymers that are cured with UV radiationare disclosed in Japanese Kokai Patent Application 5-078539.

[0010] These prior art compositions possess interesting properties, butthey do not provide compositions that exhibit the tensile strength,modulus, and compression set that is required in many commercialapplications, for example air intake manifold gaskets. There thusremains a need in the art for fluoroelastomer compositions that can becured at low temperature by low energy radiation processes and that,when cured, exhibit excellent tensile strength, modulus, and compressionset.

[0011] Similarly, chlorinated elastomers such as chlorinatedpolyethylene, chlorosulfonated polyethylene and epichlorohydrin rubber,are traditionally crosslinked thermally by either ionic or free radicalcure systems in compression molds. Extended high temperature exposure ofcurable compositions containing these polymers can be problematic due tothe tendency of these polymers to dehydrochlorinate. Because of the highcure temperatures required, these elastomers have little utility inapplications involving formation of elastomer/thermoplastic compositesthat are cured in place. Just as with ethylene alkyl acrylateelastomers, manufacture of chlorinated elastomer/thermoplastic compositearticles requires an elastomer that can be cured at a temperaturesufficiently low to preclude deformation of the thermoplastic. Lowtemperature UV cures of chlorinated polyolefin coating compositions areknown. U.S. Pat. No. 4,880,849 discloses a UV-curable chlorinatedpolyolefin coating having excellent adhesion to plastic substrates.Japanese Kokai Patent Application 63-267517 discloses UV cure ofchlorosulfonated polyethylene rubber and epichlorohydrin hose that isfirst passed through a UV irradiation apparatus and then vulcanized atelevated temperature for 30-60 minutes. However, chlorinated elastomercompositions that could be readily applied to a groove or an article intheir uncured state and that are adapted to low temperature curingtechniques are not known in the prior art.

[0012] There is thus a need for a method by which an elastomeric sealingcomposition may be applied to a substrate in an efficient, adhesive-freemanner and cured at low temperature to produce a cured seal that has anexcellent balance of tensile strength, modulus and compression set.

SUMMARY OF THE INVENTION

[0013] The present invention is directed to curable elastomericcompositions that are capable of being crosslinked at low temperatures.In particular, the present invention is directed to a thermally stable,curable elastomer composition comprising

[0014] a) 75 to 95 weight percent of an elastomer selected from thegroup consisting of

[0015] 1) copolymers comprising ethylene and a comonomer selected fromthe group consisting of C₁-C₈ alkyl esters of acrylic acid, C₁-C₈ alkylesters of methacrylic acid, and vinyl esters of C₂-C₈ carboxylic acids;

[0016] 2) alkyl acrylate polymers selected from the group consisting ofhomopolymers of C₁-C₁₀ alkyl acrylates and copolymers of C₁-C₁₀ alkylacrylates with up to 40 weight percent monovinyl monomers; and

[0017] 3) diene copolymers selected from the group consisting ofcopolymers of a diene and an unsaturated nitrile and hydrogenatedcopolymers of a diene and an unsaturated nitrile;

[0018] b) 2 to 24 weighc crosslinking agents, multifunctionalmethacrylic crosslinking agents, multifunctional cyanurate crosslinkingagents, and multifunctional isocyanurate crosslinking agents; and

[0019] c) 0.2 to 5.0 weight percent of a UV initiator

[0020] wherein the weight percentages of each of components a), b), andc) are based on the combined weight of components a), b), and c).

[0021] The invention is further directed to a process for applying aseal to an article comprising the steps of

[0022] A) blending at a temperature of between 25° C. and 250° C.

[0023] 1) 75 to 95 weight percent of an elastomer selected from thegroup consisting of

[0024] a) copolymers comprising ethylene and a comonomer selected fromthe group consisting of C₁-C₈ alkyl esters of acrylic acid, C₁-C₈ alkylesters of methacrylic acid, and vinyl esters of C₂-C₈ carboxylic acids;

[0025] b) alkyl acrylate polymers selected from the group consisting ofhomopolymers of C₁-C₁₀ alkyl acrylates and copolymers of C₁-C₁₀ alkylacrylates with up to 40 weight percent monovinyl monomers; and

[0026] c) diene copolymers selected from the group consisting ofcopolymers of a diene and an unsaturated nitrile and hydrogenatedcopolymers of a diene and an unsaturated nitrile;

[0027] 2) 2 to 24 weight percent of a multifunctional crosslinking agentselected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

[0028] 3) 0.2 to 5.0 weight percent of a UV initiator wherein the weightpercentages of each of components 1), 2), and 3) are based on thecombined weight of components 1), 2), and 3), to form a thermallystable, curable, extrudable mixture;

[0029] B) depositing said extrudable mixture on said article in theshape and thickness desired to form an uncured seal; and

[0030] C) irradiating said uncured seal with UV radiation for a timesufficient to cure said seal.

[0031] The present invention is also directed to curable fluoroelastomercompositions that are capable of being crosslinked at low temperatures.In particular, the present invention is directed to a thermally stable,curable elastomer composition comprising

[0032] A) 70 to 99 weight percent of a fluoroelastomer having at leastone cure site selected from the group consisting of 1) copolymerizedbrominated olefins, chlorinated olefins and iodinated olefins; 2)copolymerized brominated unsaturated ethers, chlorinated unsaturatedethers, and iodinated unsaturated ethers; 3) copolymerizednon-conjugated dienes and trienes and 4) iodine atoms, bromine atoms andmixtures thereof that are present at terminal positions of thefluoroelastomer chain;

[0033] B) 0.5 to 20 weight percent of a multifunctional crosslinkingagent selected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

[0034] C) 0.1 to 10 weight percent of a UV initiator

[0035] wherein the weight percentages of each of components A), B), andC) are based on the combined weight of components A), B), and C).

[0036] The invention is further directed to a process for applying aseal to an article comprising the steps of

[0037] A) blending at a temperature of between 25° C. and 250° C.

[0038] 1) 70 to 99 weight percent of a fluoroelastomer;

[0039] 2) 0.5 to 20 weight percent of a multifunctional crosslinkingagent selected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

[0040] 3) 0.1 to 10 weight percent of a UV initiator

[0041]  wherein the weight percentages of each of components 1), 2), and3) are based on the combined weight of components 1), 2), and 3), toform a thermally stable, curable, extrudable mixture;

[0042] B) depositing said extrudable mixture on said article in theshape and thickness desired to form an uncured seal; and

[0043] C) irradiating said uncured seal with UV radiation for a timesufficient to cure said seal.

[0044] The present invention is also directed to curable chlorinatedelastomer compositions that are capable of being crosslinked at lowtemperatures. In particular, the present invention is directed to athermally stable, curable elastomer composition consisting essentiallyof

[0045] A) 80 to 97 weight percent of a chlorinated elastomer selectedfrom the group consisting of chlorinated polyolefin elastomers andepichlorohydrin elastomers;

[0046] B) 2 to 19.5 weight percent of a multifunctional crosslinkingagent selected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

[0047] C) 0.2 to 5.0 weight percent of a UV initiator

[0048] wherein the weight percentages of each of components A), B), andC) are based on the combined weight of components A), B), and C).

[0049] In one embodiment, the chlorinated olefin polymer is achlorosulfonated olefin polymer.

[0050] The invention is further directed to a process for applying aseal to an article comprising the steps of

[0051] A) blending at a temperature of between 25° C. and 250° C.

[0052] 1) 80 to 97 weight percent of a chlorinated elastomer selectedfrom the group consisting of chlorinated polyolefin elastomers andepichlorohydrin elastomers;

[0053] 2) 2 to 19.5 weight percent of a multifunctional crosslinkingagent selected from the group consisting of multifunctional acryliccrosslinking agents, multifunctional methacrylic crosslinking agents,multifunctional cyanurate crosslinking agents, and multifunctionalisocyanurate crosslinking agents; and

[0054] 3) 0.2 to 5.0 weight percent of a UV initiator

[0055]  wherein the weight percentages of each of components 1), 2), and3) are based on the combined weight of components 1), 2), and 3), toform a thermally stable, curable, extrudable mixture;

[0056] B) depositing said extrudable mixture on said article in theshape and thickness desired to form an uncured seal; and

[0057] C) irradiating said uncured seal with UV radiation for a timesufficient to cure said seal.

[0058] In addition, the present invention is directed to a process forapplying a seal to an article comprising the steps of

[0059] A) blending at a temperature of between 25° C. and 250° C.

[0060] 1) 80-98 weight percent of an ethylene alpha-olefin copolymercomprising ethylene and a C₃-C₂₀ alpha-olefin;

[0061] 2) 1-19.5 weight percent of a multifunctional crosslinking agentselected from the group consisting of multifunctional acryliccrosslinking agents and multifunctional methacrylic crosslinking agents;and

[0062] 3) 0.2-5 weight percent of a UV initiator

[0063]  wherein the weight percentages of each of components 1), 2), and3) are based on the combined weight of components 1), 2), and 3), toform a thermally stable, curable, extrudable mixture;

[0064] B) depositing said extrudable mixture on said article in theshape and thickness desired to form an uncured seal; and

[0065] C) irradiating said uncured seal with UV radiation for a timesufficient to cure said seal.

[0066] The invention is also directed to cured articles produced bythese processes.

DETAILED DESCRIPTION OF THE INVENTION

[0067] The thermally stable, curable compositions of the presentinvention comprise an elastomer; a multifunctional crosslinking agent,generally an acrylic or methacrylic crosslinking agent; and a UVinitiator. These curable compositions are utilized as starting materialsin the process for applying a seal to an article that is a furtherembodiment of the invention. In preferred embodiments of the process ofthe invention, the elastomer, multifunctional crosslinking agent and UVinitiator are present as three separate components. However, the UVinitiator may be present as a chemically combined component with theelastomer. That is, the UV initiator may be chemically incorporated intothe elastomeric component as a polymer-bound photoinitiator. Suchpolymer-bound photoinitiators are disclosed, for example in U.S. Pat.No. 5,128,386 wherein a photoinitiator is copolymerized with an acrylatecopolymer.

[0068] The compositions are curable by the action of UV radiation. Theyare thermally stable at temperatures used to process uncured elastomerformulations, e.g. in mixing or extruding operations. Such temperaturesgenerally range from 25° C. to 250° C. By thermally stable is meant thatthe compositions do not spontaneously form a crosslinked network, i.e.they do not prematurely cure or scorch. That is, the viscosity of thecompositions remains constant, within ±50% of the initial value whenheated to the processing temperature, as indicated by lack of asubstantial increase in torque (i.e. an increase of less than 1 dNm)when subjected to the processing temperature for 30 minutes in a MovingDie Rheometer. The appropriate processing temperature will depend on thedecomposition temperature of the particular UV initiator andmultifunctional crosslinking agent that is employed. However, theprocessing temperature must be sufficiently high so that the curableelastomer composition flows to the degree required for the productionprocess. This temperature will generally be from 25° C. to 250° C.,preferably from 90° C. to 170° C. The compositions, when heated orsubjected to mechanical working, such as in a screw extruder, gear pump,or piston pump, are capable of viscoelastic flow and may be metered andformed into shaped articles, such as seals. These articles may then becured by exposure to UV radiation.

[0069] The elastomeric component of the thermally stable compositions ofthe invention may be any of the members of the following classes of raw(i.e. uncured) elastomeric polymers: ethylene acrylate copolymerrubbers, ethylene methacrylate copolymer rubbers, acrylate rubbers,ethylene vinyl ester elastomers, elastomeric copolymers of a diene andan unsaturated nitrile (i.e., nitrile rubber and hydrogenated nitrile),fluoroelastomers having copolymerized units of iodinated, brominated, orchlorinated cure site monomers, fluoroelastomers having copolymerizedunits of non-conjugated dienes, fluoroelastomers having bromine oriodine atoms at terminal positions of the fluoroelastomer, chlorinatedolefin elastomers, chlorosulfonated olefin elastomers, andepichlorohydrin elastomers.

[0070] One class of ethylene copolymer rubbers useful in the compositionand process of the invention is made up of two types of ethylene estercopolymers. The first type includes ethylene copolymers havingcopolymerized units of C₁-C₈ alkyl esters of acrylic acid or C₁-C₈ alkylesters of methacrylic acid. The second type includes ethylene copolymershaving copolymerized units of vinyl esters of C₂-C₈ carboxylic acids.Each of these types of copolymers includes dipolymers or higher ordercopolymers having copolymerized units of other comonomers.

[0071] When the copolymers are dipolymers, the ethylene content rangesfrom about 20-85 weight percent, preferably 30-65 weight percent.Representative examples of such compositions include copolymers ofethylene with, for example, methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate, 2-ethylhexyl acrylate, hexyl acrylate, andcopolymers of ethylene with, for example, vinyl acetate, vinylpropionate, and vinyl hexanoate. Copolymers of ethylene with, forexample, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate,2-ethylhexyl methacrylate, n-butyl methacrylate, or hexyl methacrylatemay also be employed, but ethylene acrylate copolymers and ethylenevinyl ester copolymers are preferred. Methyl acrylate, n-butyl acrylate,and vinyl acetate are among the most preferred comonomers. Thecopolymers generally have Mooney viscosities ranging from 1-60, ML 1+4(100° C.), preferably 1-20, ML 1+4 (100° C.). Blends of dipolymers mayalso be utilized.

[0072] Examples of higher order types of the foregoing elastomericcopolymers of ethylene which are suitable for use as the polymericcomponent of the compositions of the present invention includecopolymers of a) ethylene, b) alkyl acrylates, alkyl methacrylates, orvinyl esters of carboxylic acids, and c) unsaturated acids. Specificexamples include terpolymers having copolymerized units of a) ethylene,b) C₁-C₈ alkyl esters of acrylic acid, C₁-C₈ alkyl esters of methacrylicacid, or vinyl esters of C₂-C₈ carboxylic acids and c) carboxylic acidsof 3-12 carbon atoms selected from the group consisting of alpha,beta-unsaturated monocarboxylic acids; alpha, beta-unsaturateddicarboxylic acids; and monoesters of alpha, beta-unsaturateddicarboxylic acids. The ethylene content of the copolymers ranges fromabout 25-70 weight percent of the polymer, preferably 35-65 weightpercent, and the alpha, beta-unsaturated mono-or dicarboxylic acids ormonoesters of alpha, beta-unsaturated acids are present in an amountsufficient to provide 0.1-10 weight percent, preferably 0.5-5.0 weightpercent, of carboxylic acid groups. Suitable alpha, beta-unsaturatedmono-or dicarboxylic acids include monocarboxylic acids such as acrylicacid and methacrylic acid; dicarboxylic acids, such as maleic acid,fumaric acid, and itaconic acid; and monoesters of dicarboxylic acidssuch as ethyl hydrogen maleate, ethyl hydrogen fumarate, and2-ethylhexyl hydrogen maleate. Acrylic acid, methacrylic acid, and ethylhydrogen maleate are preferred. The alkyl acrylate or the vinyl estercomonomers comprise 25-70 weight percent of the polymer, preferably30-65 weight percent. Alkyl acrylates suitable for use in the polymersinclude C₁-C₈ alkyl esters of acrylic acid, for example, the methyl,ethyl, n-butyl, isobutyl, hexyl, and 2-ethylhexyl esters. Methyl, ethyl,and butyl acrylates are preferred. Methyl acrylate is most preferred.Vinyl esters of carboxylic acids suitable for use in the polymersinclude vinyl esters of carboxylic acids having 2-8 carbon atoms, forexample, vinyl acetate, vinyl propionate, vinyl hexanoate, and vinyl2-ethylhexanoate. Vinyl acetate is preferred. Mooney viscosities, ML 1+4(100° C.), of these copolymers generally range from 1-50, preferably1-20. Representative examples of such copolymers include terpolymers andtetrapolymers such as ethylene/methyl acrylate/methacrylic acidcopolymers; ethylene/methyl acrylate/ethyl hydrogen maleate copolymers;ethylene/acrylic acid/vinyl acetate copolymers; ethylene/butylacrylate/acrylic acid copolymers; ethylene/vinyl acetate/methacrylicacid copolymers; ethylene/fumaric acid/methyl acrylate copolymers;ethylene/methyl acrylate/carbon monoxide/methacrylic acid copolymers;and ethylene/ethyl hydrogen maleate/carbon monoxide/vinyl acetatecopolymers. Copolymer blends may also be utilized.

[0073] Another polymer type in this class of elastomeric ethylenecopolymers suitable for use in the practice of the invention containscopolymerized units of ethylene, an acrylic ester or vinyl ester,glycidyl acrylate or methacrylate, and optionally, carbon monoxide.Generally, such compositions contain from 30-70 weight percent ethylene,25-65 weight percent acrylic or vinyl ester, 2-10 weight percentglycidyl acrylate or methacrylate, and 0-15 weight percent carbonmonoxide, the weight percentages adding up to 100 weight percent.Copolymers of ethylene, acrylate ester, and glycidyl methacrylate arepreferred. Representative alkyl acrylates and alkyl acrylates that areused as comonomers include methyl acrylate, ethyl acrylate, propylacrylate, n-butyl acrylate, isobutyl acrylate, and hexyl acrylate.Representative copolymers include ethylene/methyl acrylate/glycidylmethacrylate, ethylene/n-butyl acrylate/glycidyl methacrylate,ethylene/vinyl acetate/glycidyl methacrylate, and ethylene/methylacrylate/carbon monoxide/glycidyl methacrylate.

[0074] A further polymer type in this class of elastomeric ethylenecopolymers suitable for use in the practice of the invention containscopolymerized units of a) ethylene; b) vinyl acetate, a C₁-C₈ alkylacrylate or a C₁-C₈ alkyl methacrylate; and c) carbon monoxide or sulfurdioxide. The vinyl acetate, alkyl acrylate or alkyl methacrylate contentof the copolymer is generally 20-50 weight percent and the carbonmonoxide or sulfur dioxide content is generally 5-40 weight percent.Examples of such copolymers include ethylene/vinyl acetate/carbonmonoxide; ethylene/n-butyl acrylate/carbon monoxide; ethylene/methylacrylate/carbon monoxide; ethylene/ethyl hydrogen maleate/carbonmonoxide/vinyl acetate.

[0075] Both the dipolymers and higher copolymers described above aregenerally prepared by continuous copolymerization of ethylene and thecomonomers in a stirred reactor in the presence of at least one freeradical initiator at temperatures of from about 100° C. to 300° C. andat pressures of from about 130 to 350 MPa, generally as described inU.S. Pat. No. 3,883,472. Most preferably the copolymers are alsoprepared in the presence of about 2-25 weight percent methanol oracetone so that reactor fouling is decreased or eliminated.

[0076] The elastomeric component may also be selected from the class ofacrylate rubbers comprising homopolymers or copolymers of C₁-C₁₀ alkylacrylates. Preferred alkyl acrylates include ethyl acrylate, butylacrylate, and 2-ethylhexyl acrylate. Copolymeric acrylate rubberscontain copolymerized units of up to 40 weight percent monovinylmonomers, for example, styrene, acrylonitrile, vinylbutyl ether, acrylicacid, and C₁-C₁₀ alkyl acrylates different from the principal alkylacrylate comonomer. Such copolymers are available commercially, forexample, Hytemp® acrylate rubbers (acrylic homopolymer and copolymerrubbers available from Nippon Zeon, KK), and Toacron® AR-601 acrylaterubbers (polyethylacrylate polymers, available from Toa Paint, KK.).

[0077] Further, the elastomeric component may be a copolymer of a dieneand an unsaturated nitrile. The diene may be, for example, butadiene.The nitrile is preferably acrylonitrile. Such copolymers are known asnitrile rubbers and are commercially available. They generally haveacrylonitrile contents of 18-50 wt. %. Hydrogenated nitrile rubbers arealso suitable for use in the compositions of the invention.

[0078] Fluoroelastomers suitable for use as the elastomeric component ofthe compositions of the invention include fluoroelastomers comprisingcopolymerized units of one or more monomers containing fluorine, such asvinylidene fluoride, hexafluoropropylene, 1-hydropentafluoropropylene,2-hydropentafluoropropylene, tetrafluoroethylene,chlorotrifluoroethylene, and perfluoro(alkyl vinyl) ether, as well asother monomers not containing fluorine, such as ethylene, and propylene.Elastomers of this type are described in Logothetis, Chemistry ofFluorocarbon Elastomers, Prog. Polym. Sci., Vol. 14, 251-296 (1989). Thepolymers may be prepared by polymerization of the appropriate monomermixtures with the aid of a free radical generating initiator either inbulk, in solution in an inert solvent, in aqueous emulsion or in aqueoussuspension. The polymerizations may be carried out in continuous, batch,or in semi-batch processes. General preparative processes are disclosedin the Logothetis article and in U.S. Pat. Nos. 4,281,092; 3,682,872;4,035,565; 5,824,755; 5,789,509; 3,051,677; and 2,968,649.

[0079] Specific examples of such fluoroelastomers include copolymers ofvinylidene fluoride and hexafluoropropylene and, optionally,tetrafluoroethylene; copolymers of vinylidene fluoride andchlorotrifluoroethylene; copolymers of vinylidene fluoride,hexafluoropropylene, tetrafluoroethylene and chlorotrifluoroethylene;copolymers of tetrafluoroethylene and propylene; and copolymers oftetrafluoroethylene and perfluoro(alkyl vinyl) ether, preferablyperfluoro(methyl vinyl) ether. Each of the fluoroelastomers of thecomposition of the invention also comprises at least one halogenatedcure site or a reactive double bond resulting from the presence of acopolymerized unit of a non-conjugated diene. The halogenated cure sitesmay be copolymerized cure site monomers or halogen atoms that arepresent at terminal positions of the fluoroelastomer polymer chain. Thecure site monomers, reactive double bonds or halogenated end groups arecapable of reacting to form crosslinks. The cure site monomers areselected from the group consisting of brominated, chlorinated, andiodinated olefins; brominated, chlorinated, and iodinated unsaturatedethers and non-conjugated dienes.

[0080] The brominated cure site monomers may contain other halogens,preferably fluorine. Examples are bromotrifluoroethylene,4-bromo-3,3,4,4-tetrafluorobutene-1 and others such as vinyl bromide, 1-bromo-2,2-difluoroethylene, perfluoroallyl bromide,4-bromo-1,1,2-trifluorobutene, 4-bromo-1,1,3,3,4,4,-hexafluorobutene,4-bromo-3-chloro-1,1,3,4,4-pentafluorobutene,6-bromo-5,5,6,6-tetrafluorohexene, 4-bromoperfluorobutene-1 and3,3-difluoroallyl bromide. Brominated unsaturated ether cure sitemonomers useful in the invention include ethers such as2-bromo-perfluoroethyl perfluorovinyl ether and fluorinated compounds ofthe class CF₂Br—R_(f)—O—CF═CF₂, such as CF₂BrCF₂O—CF═CF₂, andfluorovinyl ethers of the class ROCF═CFBr or ROCBr═CF₂, where R is alower alkyl group or fluoroalkyl group, such as CH₃OCF═CFBr orCF₃CH₂OCF═CFBr.

[0081] Iodinated olefins may also be used as cure site monomers.Suitable iodinated monomers include iodinated olefins of the formula:CHR═CH—Z—CH₂CHR—I, wherein R is —H or —CH₃; Z is a C₁-C₁₈(per)fluoroalkylene radical, linear or branched, optionally containingone or more ether oxygen atoms, or a (per)fluoropolyoxyalkylene radicalas disclosed in U.S. Pat. No. 5,674,959. Other examples of usefuliodinated cure site monomers are unsaturated ethers of the formula:I(CH₂CF₂CF₂)_(n)OCF═CF₂ and ICH₂CF₂O[CF(CF₃)CF₂O]_(n)CF═CF₂, and thelike, wherein n=1-3, such as disclosed in U.S. Pat. No. 5,717,036. Inaddition, suitable iodinated cure site monomers including iodoethylene,4-iodo-3,3,4,4-tetrafluorobutene-1;3-chloro-4-iodo-3,4,4-trifluorobutene;2-iodo-1,1,2,2-tetrafluoro-1-(vinyloxy)ethane;2-iodo-1-(perfluorovinyloxy)-1,1,-2,2-tetrafluoroethylene;1,1,2,3,3,3-hexafluoro-2-iodo-1-(perfluorovinyloxy)propane; 2-iodoethylvinyl ether; 3,3,4,5,5,5-hexafluoro-4-iodopentene; andiodotrifluoroethylene are disclosed in U.S. Pat. No. 4,694,045.

[0082] Examples of non-conjugated diene cure site monomers include1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene and others, such as thosedisclosed in Canadian Patent 2,067,891. A suitable triene is8-methyl-4-ethylidene-1,7-octadiene.

[0083] Of the cure site monomers listed above, preferred compoundsinclude4-bromo-3,3,4,4-tetrafluorobutene-1,4-iodo-3,3,4,4-tetrafluorobutene-1,and bromotrifluoroethylene.

[0084] Additionally, or alternatively, iodine, bromine or mixturesthereof may be present at the fluoroelastomer chain ends as a result ofthe use of chain transfer or molecular weight regulating agents duringpreparation of the fluoroelastomers. Such agents includeiodine-containing compounds that result in bound iodine at one or bothends of the polymer molecules. Methylene iodide;1,4-diiodoperfluoro-n-butane; and 1,6-diiodo-3,3,4,4,tetrafluorohexaneare representative of such agents. Other iodinated chain transfer agentsinclude 1,3-diiodoperfluoropropane; 1,4-diiodoperfluorobutane;1,6-diiodoperfluorohexane; 1,3-diiodo-2-chloroperfluoropropane;1,2-di(iododifluoromethyl)-perfluorocyclobutane;monoiodoperfluoroethane; monoiodoperfluorobutane;2-iodo-1-hydroperfluoroethane, etc. Particularly preferred arediiodinated chain transfer agents. Examples of brominated chain transferagents include 1-bromo-2-iodoperfluoroethane;1-bromo-3-iodoperfluoropropane; 1-iodo-2-bromo-1,1-difluoroethane andothers such as disclosed in U.S. Pat. No. 5,151,492.

[0085] Copolymers of ethylene, tetrafluoroethylene, perfluoro(alkylvinyl) ether and a bromine-containing cure site monomer, such as thosedisclosed by Moore, in U.S. Pat. No. 4,694,045 are suitable for use inthe present invention. Copolymers of tetrafluoroethylene andperfluoro(alkyl vinyl) ether commonly containing fluorinated nitrilecure sites, for example perfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene)and others disclosed in U.S. Pat. No. 4,983,697 may also be used. Otheruseful fluoroelastomers containing brominated or iodinated olefin curesite monomers are described in U.S. Pat. Nos. 4,035,565; 4,564,662;4,745,165; 4,694,045; 4,948,852; and 4,973,633.

[0086] Each of these classes of copolymers includes dipolymers or higherorder copolymers having copolymerized units of other comonomers.

[0087] It has been found that raw fluoroelastomers having Mooneyviscosities in the range of 5-150, ML 1+4 (121° C.), preferably 10-70,ML 1+4 (121° C.) are particularly useful in the compositions of thepresent invention. Those compositions wherein the fluoroelastomer has aMooney viscosity within the preferred range exhibit an optimum balanceof processability and tensile properties.

[0088] It has also been found that compositions containingfluoroelastomers having levels of copolymerized cure site monomer unitswithin the range of 0.05-10.0 wt. %. exhibit enhanced cure state.

[0089] Chlorinated olefin polymers are also suitable for use as theelastomeric component of the compositions of the invention. Thechlorinated olefin polymers also specifically include chlorosulfonatedolefin polymers. By olefin polymers is meant homopolymers and copolymersof C₂-C₈ alpha-monoolefins, including graft copolymers. The copolymersmay be dipolymers or higher order copolymers, such as terpolymers ortetrapolymers. The olefin polymers may be branched or unbranched and maybe prepared by free radical processes, Ziegler-Natta catalysis orcatalysis with metallocene catalyst systems. for example those disclosedin U.S. Pat. Nos. 5,272,236 and 5,278,272. Particularly useful examplesof olefin polymers include homopolymers of C₂-C₃ alpha monoolefins,copolymers of ethylene and carbon monoxide, and copolymers of ethyleneand at least one ethylenically unsaturated monomer selected from thegroup consisting of C₃-C₂₀ alpha monoolefins, C₁-C₁₂ alkyl esters ofunsaturated C₃-C₂₀ monocarboxylic acids, unsaturated C₃-C₂₀ mono- ordicarboxylic acids, anhydrides of unsaturated C₄-C₈ dicarboxylic acids,and vinyl esters of saturated C₂-C₁₈ carboxylic acids. Specific examplesof these polymers include polyethylene, polypropylene, ethylene vinylacetate copolymers, ethylene acrylic acid copolymers, ethylenemethacrylic acid copolymers, ethylene methyl acrylate copolymers,ethylene methyl methacrylate copolymers, ethylene n-butyl methacrylatecopolymers, ethylene glycidyl methacrylate copolymers, graft copolymersof ethylene and maleic anhydride, graft copolymers of propylene andmaleic anhydride, and copolymers of ethylene with propylene, butene,3-methyl-1-pentene, hexene, or octene. Preferred olefin polymers arepolyethylene, ethylene propylene copolymers, ethylene butene copolymers,ethylene octene copolymers, copolymers of ethylene and acrylic acid,copolymers of ethylene and methacrylic acid, and copolymers of ethyleneand vinyl acetate. The olefin polymers have number average molecularweights within the range of 1,000 to 300,000, preferably from 50,000 to300,000. The chlorinated and chlorosulfonated olefin polymers havechlorine contents of from about 15 weight percent to about 70 weightpercent. The chlorosulfonated olefin polymers have sulfur contents of0.5-10 weight percent, preferably 1-3 weight percent.

[0090] The chlorinated or chlorosulfonated olefin polymers may beprepared from the olefin polymers by free radical initiated chlorinationand chlorosulfonation. Chlorination of the olefin polymers may takeplace at temperatures of 50° C. -150° C. and at pressures of 1-10atmospheres using gaseous chlorine as the chlorinating agent. Insolution chlorination, the reaction medium is an inert solvent, forexample carbon tetrachloride, chlorinated benzene, chloroform orfluorobenzene. Alternatively, slurry chlorination in aqueous or organicsuspension can be used. Fluidized bed processes are also known, as wellas melt processes. Chlorosulfonation of the olefin polymer startingmaterials may take place in solution, under similar conditions,utilizing gaseous chlorine and sulfur dioxide, sulfuryl chloride, or acombination of chlorine, sulfur dioxide and sulfuryl chloride.Commercially available chlorinated and chlorosulfonated olefin polymersinclude Tyrin®chlorinated polyethylene, Hypalon®chlorosulfonatedpolyethylene, and Acsium®chlorosulfonated polyethylene, all availablefrom DuPont Dow Elastomers L.L.C.

[0091] Epichlorohydrin elastomers that are suitable for use as theelastomeric component of the compositions of the invention include bothpolyepichlorohydrin homopolymers and copolymers comprising copolymerizedunits of epichlorohydrin and ethylene oxide. Terpolymers containing curesite monomers, such as allyl glycidyl ether, may also be used. Suchcompositions generally contain about 20-45 wt. % chlorine. Commerciallyavailable examples include Epichlomer®rubber manufactured by DaisoEpichlo Rubber Co., Ltd., Japan and Hydrin®epichlorohydrin rubbermanufactured by Nippon Zeon Co., Ltd., Japan.

[0092] The elastomeric component of the compositions of the inventionmay be a blend of elastomers as well as a single elastomer. The blendsmay be mixtures of polymers of the same class, for example, a brominatedfluoroelastomer and an iodinated fluoroelastomer, or they may bemixtures of more than one type of elastomer, for example a chlorinatedpolyolefin rubber and an ethylene copolymer rubber. Blends wherein onlyone elastomer is capable of cure by exposure to UV radiation are alsocontemplated by the invention. Blend compositions would be particularlyuseful for balancing physical properties. For example, it would bedesirable to balance state of cure with fuel resistance by blendingfluoroelastomers with epichlorohydrin rubbers. In other circumstances,blends of costly polymers with less expensive polymers often yield acombination of properties that are adequate for less demandingapplications. In this context, blends of fluoroelastomers and nitrilerubber or fluoroelastomers and ethylene acrylate copolymer elastomerswould be suitable for use as the elastomeric component of thecompositions of the invention. The Mooney viscosities of the blends willpreferably be within the range of 1-150 because within this range theblends will be suitable for use in the process of the present inventionfor producing general rubber articles, such as seals.

[0093] In addition to an elastomeric component, the curable compositionsof the invention also include at least one multifunctional crosslinkingagent. Preferably the multifunctional crosslinking agent will be anacrylic or methacrylic crosslinking agent. In addition, it may be amultifunctional cyanurate or multifunctional isocyanurate, such astriallyl isocyanurate or triallyl cyanurate. By multifunctional acrylicor methacrylic crosslinking agent is meant an ester that is a reactionproduct of a polyhydroxylic compound, generally a polyhydroxylicalcohol, and acrylic acid or methacrylic acid, wherein the crosslinkingagent has at least two carbon-carbon double bonds. Such compositions arecommonly referred to in the art as multifunctional acrylates ormultifunctional methacrylates. Typical multifunctional acrylates andmethacrylates have molecular weights of 150 to 1,000 and contain atleast two polymerizable unsaturated groups per molecule.

[0094] Representative multifunctional acrylic crosslinking agentsinclude acrylates and methacrylates such as ethylene glycol diacrylate;ethylene glycol dimethacrylate; 1,6-hexanediol diacrylate;1,6-hexanediol dimethacrylate; 1,4-butanediol diacrylate;pentaerythritol triacrylate; pentaerythritol tetraacrylate;dipentaerythritol pentaacrylate, methoxy-1,6-hexanediolpentaerythritoltriacrylate; trimethylolpropane triacrylate; tetraethylene glycoldiacrylate; polymethacrylate urethanes; epoxy acrylates; polyesteracrylate monomers and oligomers; trimethylolpropane propoxylatetriacrylate; poly-n-butyleneoxide glycol diacrylates; and bisphenol Aalkylene oxide adduct diacrylates. Trimethylolpropane triacrylate andtrimethylolpropane trimethacrylate are preferred crosslinking agentsbecause these compounds are readily available. In addition, compressionset and crosslink density are enhanced in compositions containing thesecrosslinking agents compared to compositions containing difunctionalacrylates, such as diethylene glycol dimethacrylate.

[0095] The multifunctional acrylic and methacrylic crosslinking agentsare capable of homopolymerization when irradiated. Thus, when thecurable compositions of the invention that contain multifunctionalacrylates or methacrylates are exposed to UV radiation, two reactionsoccur simultaneously. The multifunctional crosslinking agent reacts withthe elastomeric polymer component to form interchain and intrachaincrosslinks, resulting in a rubber matrix. In addition, excessmultifunctional crosslinking agent will homopolymerize and form aninterpenetrating network which acts to reinforce the rubber matrix, muchin the same manner as fillers reinforce elastomers. It is thereforepossible to control the hardness of the final cured product by adjustingthe proportion of multifunctional crosslinker present in the curablecomposition. In general, difunctional acrylates and methacrylates areless efficient crosslinking agents compared to their analogues havinghigher functionalities. Consequently, crosslinking agents of the classhaving higher functionalities are preferred for purposes of the presentinvention.

[0096] Elastomeric materials compounded and cured according to methodscommonly used in rubber processing technology generally contain carbonblack or mineral fillers as reinforcing agents. Reinforcement isreflected in properties such as hardness, modulus, and tensile strength.Generally, reinforced elastomers are characterized by non-linearstress/strain dependence. In contrast, non-reinforced elastomercompositions are characterized by an initial stress build-up at lowdeformation which does not substantially increase at higher deformation.Further, non-reinforced elastomer compositions tend to break atrelatively low ultimate tensile strength.

[0097] Use of fillers in UV-initiated reactions would normally beexpected to interfere with the UV curing process. However, the presentprocess permits curing of translucent compositions. Thus, thecompositions of the present invention may contain a limited amount offillers, generally no more than 15 parts by weight per 100 partspolymer. Reinforcement is effected simultaneously with crosslinking byformation of an interpenetrating network. The resultant product exhibitsstress/strain behavior that is more linear than that of traditionalelastomers which contain fillers which are not chemically bound to theelastomer matrix.

[0098] The amount of multifunctional crosslinking agent present in thecompositions of the invention will depend on the particular elastomerused. Generally, the amount ranges from 0.5 to 25 weight percent, basedon the combined weight of polymer, multifunctional crosslinking agent,and UV initiator.

[0099] The third component of the curable compositions of the inventionis a UV initiator. It may be selected from those organic chemicalcompounds conventionally employed to promote UV-initiated formation ofradicals either by intramolecular homolytic bond cleavage or byintermolecular hydrogen abstraction. Such agents include organiccompounds having aryl carbonyl or tertiary amino groups. Among thecompounds suitable for use are benzophenone; acetophenone; benzil;benzaldehyde; o-chlorobenzaldehyde; xanthone; thioxanthone;9,10-anthraquinone; 1-hydroxycyclohexyl phenyl ketone;2,2-diethoxyacetophenone; dimethoxyphenylacetophenone; methyldiethanolamine; dimethylaminobenzoate;2-hydroxy-2-methyl-1-phenylpropane-1-one; 2,2-di-sec-butoxyacetophenone;2,2-dimethoxy-1,2-diphenylethan-1-one; benzil dimethoxyketal; benzoinmethyl ether; and phenyl glyoxal. Upon exposure to UV radiation, avariety of photochemical transformations may occur, for example, the UVinitiator may form free radical reactive fragments that react with theacrylate end groups of the multifunctional acrylic or methacryliccrosslinking agent. This initiates crosslinking of the polymer as wellas homopolymerization of the acrylic or methacrylic crosslinking agent.A preferred UV initiator is 1-hydroxycyclohexyl phenyl ketone because ofthe rapidity with which it generates free radicals when exposed to UVradiation. Mixtures of UV initiators may also be used. This is oftendesirable because it provides more efficient production of radicals incertain cases. In general, the UV initiator will be present in an amountof 0.1 to 10.0 weight percent, based on the total weight of polymer,multifunctional crosslinking agent, and UV initiator. However, it ispreferable to use between 0.5-2.5 weight percent UV initiator, mostpreferably 0.5-1.0 weight percent UV initiator, based on total weight ofpolymer, crosslinking agent and UV initiator, because high levels ofphotoinitiator tend to interfere with penetration and do notsubstantially contribute to the overall crosslink density. Within theranges disclosed herein, there is an optimum level of photoinitiator foreach particular combination of uncured gum elastomer and crosslinkingagent. These optimum levels can be readily determined by one skilled inthe art. For example, hydrogenated nitrile rubber will generally requirea higher level of photoinitiator than a copolymer of ethylene, methylacrylate, and ethyl hydrogen maleate. Higher levels of photoinitiatorincrease the crosslink density at the surface of the cured composition.Low levels of photoinitiators can result in better (i.e. lower)compression sets of samples that are several millimeters thick.

[0100] In addition, for purposes of the present invention, theprocessing temperature must not exceed the temperature at which thermaldegradation of the UV initiator occurs. In some cases such degradationwould result in scorchy compositions due to formation of free radicals.This is so because thermally-induced fragmentation of the initiatorwithin the processing equipment results in premature crosslinking of theelastomer. In other instances, slow curing compositions would result dueto inactivation of the initiator. Degradation temperatures will differfor each particular UV initiator. Depending upon the type of rubber andthe amount of additives, the processing temperature will range frombetween 25° and 250° C. It is an object of the invention to providestable elastomeric compositions which can be applied to a substrate attemperatures of up to 250° C. A further practical limitation on theprocessing temperature is that the temperature must not exceed thesoftening point of the substrate to which it is applied.

[0101] The elastomeric component, multifunctional crosslinking agentcomponent, and UV initiator component are present in the compositions ofthe present invention in specific relative ratios. When the elastomericcomponent of the composition is an ethylene copolymer elastomer anacrylate rubber or a nitrile rubber, the elastomer is present in anamount of 75-95 weight percent, based on the total weight of elastomer,crosslinking agent, and UV initiator. The multifunctional crosslinkingagent is present in an amount of 2 to 24 weight percent, based on thetotal weight of elastomer, crosslinking agent, and UV initiator.Finally, the UV initiator is present in an amount of 0.2 to 5.0 weightpercent based on the total weight of elastomer, crosslinking agent, andUV initiator. Preferably, the elastomeric component will be present inan amount of from 87-95 weight percent, based on the total weight ofelastomer, crosslinking agent, and UV initiator. The level ofcrosslinker determines compression set resistance and hardness in thecurable composition of the invention. If less than 2 weight percentcrosslinker is present, a composition having low hardness and poorcompression set resistance is formed. Greater than 30 weight percentcrosslinker results in production of a composition of hardness greaterthan 70 Shore A. Such compositions are generally unsuitable for use insealing, especially gasketing, applications. The particular componentrange selected will thus depend on the specific end use contemplated.Preferred compositions contain 5-20 weight percent multifunctionalcrosslinking agent, and most preferred compositions contain 5-15 weightpercent multifunctional crosslinking agent, based on the combined weightof polymer, multifunctional crosslinking agent and UV initiator.

[0102] When the elastomeric component of the composition is afluoroelastomer, the elastomer is present in an amount of 70-99 weightpercent, based on the total weight of elastomer, crosslinking agent, andUV initiator. The multifunctional crosslinking agent is present in anamount of 0.5-20 weight percent, based on the total weight of elastomer,crosslinking agent, and UV initiator. Finally, the UV initiator ispresent in an amount of 0.1-10 weight percent based on the total weightof elastomer, crosslinking agent, and UV initiator. Preferably, theelastomeric component will be present in an amount of from 75-95 weightpercent, based on the total weight of elastomer, crosslinking agent, andUV initiator. The level of crosslinker determines compression setresistance and hardness in the curable composition of the invention.Preferably the multifunctional crosslinker is present in an amount of4-15 weight percent based on the weight of elastomer, crosslinker and UVinitiator. If less than about 4 weight percent crosslinker is present, acomposition having fairly low hardness and relatively high compressionset resistance is formed. Greater than about 15 weight percentcrosslinker results in unacceptably high modulus, very low elongation atbreak, and poor compressability of the cured composition. Suchcompositions are generally unsuitable for use in sealing, especiallygasketing, applications. The particular component range selected willthus depend on the specific end use contemplated.

[0103] When chlorinated olefin polymers, chlorosulfonated olefinpolymers or epichlorohydrin rubbers are used as the elastomericcomponent of the composition, the elastomer is present in an amount of80-97 weight percent, based on the total weight of elastomer,crosslinking agent, and UV initiator. The multifunctional crosslinkingagent is present in an amount of 2-19.5 weight percent, based on thetotal weight of elastomer, crosslinking agent, and UV initiator. The UVinitiator is present in an amount of 0.2-5.0 weight percent based on thetotal weight of elastomer, crosslinking agent, and UV initiator.Preferably, the elastomeric component will be present in an amount offrom 85-95 weight percent, based on the total weight of elastomer,crosslinking agent, and UV initiator. Preferably, the crosslinker willbe present in an amount of 3-15 weight percent, based on the totalweight of elastomer, crosslinking agnet and UV initiator. If less than 3weight percent crosslinker is present, a cured composition havingrelatively high compression set generally results. Greater than 15weight percent crosslinker results in a high level of hompolymerizedacrylic or methacrylic crosslinker producing a highly crosslinkedelastomeric matrix of high hardness, low compressability and lowelongation at break. As with the other compositions of the invention,the particular component range selected will thus depend on the specificend use contemplated.

[0104] Various additives, commonly used in rubber compounding may beincorporated into the compositions of the present invention to modify,stabilize, and reinforce them. Preferably, such additives will be usedin amounts which do not interfere substantially with the crosslinkingreaction of the uncured polymeric component. For example, if largeamounts of fillers that are opaque to UV light are utilized, the filledcompositions will not cure evenly throughout, or only the surface of thecomposition will be cured. Usually, fillers may be employed in amountsof up to about 15 parts per hundred parts of elastomer. Typical examplesinclude non-black fillers such as minerals or glass fibers. Polymericfillers of high reinforcing efficiency, such as polytetrafluoroethyleneand aramid fibers, may also be used, generally at low levels. It ispreferable that the presence of additives does not raise the viscosityof the curable composition used in the process of the invention to morethan ML 1+4 (100° C.) of 150 or lower it to less than ML 1+4 (100° C.)of 1. Compositions outside this range are not suitable for the gasketingin place process of the invention.

[0105] When the polymeric component is a fluoroelastomer, preferredcurable compositions of the present invention will include 0.01-2.0parts by weight per hundred parts by weight fluoroelastomer of anorganotin hydride. Compositions wherein this additive is present exhibitexcellent cure profiles. That is, the cure rate increases rapidly afterinitiation and the cure state remains high throughout the cure process.Preferably 0.1-1 parts by weight of the organotin hydride will be usedper 100 parts by weight fluoroelastomer. Tri-n-butyltin hydride ispreferred.

[0106] When ethylene acrylate copolymers are utilized as the polymericcomponent, heat and oxidation resistance of the compositions of theinvention are preferably enhanced by incorporation of antioxidants.Generally, aromatic antioxidants are utilized, especially aromaticamines. Due to their protective action, these compounds interfere to acertain extent with the free radical crosslinking reaction initiated byUV radiation. In the absence of antioxidants, the compositions aresubject to surface cracking when exposed to temperatures of 150° C. forperiods of several days. Among the most useful antioxidants are4,4′-bis(α, α-dimethyl-benzyl) diphenylamine and blends of4,4′-bis(α,α-dimethylbenzyl)diphenylamine with 4-(α,α-dimethylbenzyl)diphenylamine. Hindered phenols may be employed, butthey interfere more with the curing reaction than do the aromaticamines. Antioxidants are usually incorporated at a level of between0.5-2 parts per 100 parts polymer. Other additives may also beincorporated into the compositions of the invention, for exampleplasticizers, adhesion promoters, flame retardants, and process aidscommonly used in rubber compounding.

[0107] Small amounts of inhibitors may also be present in thecompositions of the invention as a result of the presence of theseadditives in commercial samples of acrylic or methacrylic crosslinkingagents. The inhibitors are generally present in low amounts, for examplebelow 1500 ppm (parts per million, based on the weight of thecrosslinking agent). They act to prevent thermally inducedpolymerization of the crosslinking agents during storage and shipment.

[0108] The compositions of the invention are particularly suited formanufacture of elastomeric seals and gaskets in situ using a techniquewe refer to herein as gasketing in place. According to this technique, acurable elastomeric composition is heated to a temperature of 25°-250°C., preferably 90° C.-170° C. The heated composition is then meteredonto a substrate to form an uncured seal of a desired thickness which isthen cured. Thus, the seal is formed in place directly on the object tobe sealed, rather than in a separate molding step. Typically, uncuredseals are formed in thicknesses of 1-15 mm, preferably in thicknesses of2-8 mm.

[0109] Robotized hot melt equipment may be used to apply gaskets inplace. In one embodiment of the process of the present invention, acurable composition comprising a low viscosity elastomer component,multifunctional crosslinking agent, and UV initiator, is introduced to adrum having a heated platen and piston. The composition, when heated,becomes soft and extrudable. It is forced out of the drum by the actionof the piston, generally at relatively low pressures, typically lessthan 5.0 bars (i.e. 0.5 MPa). The composition is then fed by gear orpiston pumping through heated tubing to an application gun fitted to amultidimensional industrial robot capable of precise and rapid metering.In this way, the composition can be introduced into a groove of a partsuch as a thermoplastic article that has just been produced, for exampleby molding. The bead of uncured elastomer in the groove solidifiesrapidly as it cools and forms an uncured sealing element. The groove canbe in a part made from other materials as well, including but notlimited to metal. Alternatively, the composition can be deposited ontothe exterior of an object to form a seal. This hot melt applicationmethod is preferred for low viscosity elastomers, generally of Mooneyviscosity 1-20 ML 1+4 (100° C.), especially ethylene acrylic elastomers,polyacrylate rubbers, nitrite rubbers, or ethylene vinyl acetateelastomers. The method permits extrusion from a drum using relativelylow pressures. Continuous feeding and metering pumps are capable ofhandling compositions of the invention having viscosities up to 1000Pa.s. Hot melt equipment may be used for compositions having somewhathigher viscosities, for example ML 1+4 (100° C.) of 70, by employing anextruder to introduce the composition into the heated tubing. Theviscosity thereupon decreases, permitting formation of seals from thehigher viscosity compositions.

[0110] In another embodiment of the process of the invention, relativelyhigh viscosity compositions or compositions of relatively low heatresistance may be formed into uncured seals by the gasketing in placetechnique. Instead of using hot melt equipment, screw extruders areexclusively utilized to deliver the elastomeric composition to thearticle to be sealed. This technique is particularly useful whenfluoroelastomers and chlorinated elastomers of Mooney viscosity 10-90[ML 1+10 (121° C.)] are employed as the elastomeric component of theinvention. An extruder that is used in combination with a flexible armto apply a bead of uncured elastomer to a groove is particularlypreferred for such gasketing in place processes. This differs fromconventional extruder technology in that the extruder is not utilized toform the finished part. Instead, it pumps the uncured elastomercomposition to a robotized application head that meters the compositionand deposits it at the location to be sealed. Use of screw extrudersresults in relatively high energy input to the polymer compared withprocesses which utilize hot melt equipment. In order to minimizeelastomer degradation in the extruder, the extrusion process must notcause the temperature of the compound to rise above 250° C. Thisgenerally requires slow extrusion speeds. Consequently, extrusionprocesses are generally slower methods of manufacture. Further, suchequipment requires high investment costs. Those skilled in the art willrecognize that the appropriate temperature for extrusion will bedependent on the viscosity of the uncured elastomer, the molecularweight of the uncured elastomer, the level of crosslinking agent, thedecomposition temperature of the photoinitiator and the volatilizationtemperature of the crosslinking agent and will select a value within therange of 25°-250° C. that is optimum for the particular circumstances.

[0111] The gasketing process of the present invention may be employedfor manufacture of seals and gaskets using the compositions of thepresent invention or other curable elastomer compositions. Generally,the elastomer component will be present in an amount of from 70-99 partsby weight, the multifunctional crosslinker will be present in an amountof 0.1-10 parts by weight, and the UV initiator will be present in anamount of 0.1-10 parts by weight, all based on the combined weight ofelastomer, crosslinker, and UV initiator. For example, the processes maybe used to form gaskets from fluoroelastomer compositions comprising afluoroelastomer, multifunctional crosslinker and UV initiator whereinthe fluoroelastomer component of the composition does not contain acopolymerized brominated, iodinated, chlorinated or non-conjugated dienecure site monomer or iodinated or brominated polymer end groups. Suchcopolymers are commercially available and include dipolymers ofvinylidene fluoride with hexafluoropropylene; terpolymers of vinylidenefluoride, hexafluoropropylene, and tetrafluoroethylene; and copolymersof tetrafluoroethylene and propylene. In addition, ethylene alpha-olefinelastomers, such as elastomeric copolymers and interpolymers of ethylenewith one or more comonomers selected from propylene, 1-butene, 1-hexene,1-octene, 4-methyl-1-penetene, and other C₃-C₂₀ alpha-olefins, aresuitable elastomeric components in the UV curable composition.Elastomeric copolymers of ethylene, a C₃-C₈ olefin, and a diene may alsobe used in the process of the invention. These copolymers can beterpolymers, tetrapolymers or higher order copolymer elastomers of theethylene/C₃-C₈ alpha olefin/diene type. These elastomers are copolymersof ethylene, a C₃-C₈ alpha-olefin and at least one non-conjugated diene.They may, in addition, contain a minor amount, generally up to 10 weightpercent, of at least one other diene or triene having copolymerizabledouble bonds. Preferred C₃-C₈ alpha-olefins are propylene and butene.The non-conjugated dienes of the first type include 1,4-hexadiene;2-methyl-1,5-hexadiene; vinyl norbornene;8-methyl-4-ethylidene-1,7-octadiene; 1,9-octadecadiene;dicyclopentadiene; tricyclopentadiene; 5-ethylidene-2-norbornene; or5-methylene-2-norbornene. Preferred dienes having one reactive doublebond are 1,4-hexadiene, dicyclopentadiene and ethylidene norbornene. Thenon-conjugated dienes of the second type include norbornadiene;1,4-pentadiene; 1,5-hexadiene; 1,7-octadiene; ; 1,2-heneicosadiene;or5-(5-hexenyl)-2-norbornene, preferably norbornadiene. These polymersare generally produced by polymerization in the presence ofZiegler-Natta catalysts or by polymerization in the presence ofmetallocene catalysts. Preparative techniques for ethylene alpha-olefinelastomers prepared in the presence of metallocene catalysts may befound in U.S. Pat. Nos. 5,278,272 and 5,272,236. Typical ethylenealpha-olefin copolymers and EPDM elastomers are commercially availableas Engage®polyolefin elastomers and Nordel®hydrocarbon rubbers fromDuPont Dow Elastomers L.L.C. The proportion of elastomer,multifunctional crosslinking agent, and UV initiator will generally bein the weight ratio of 70-99:0.5-19.5:01-10, respectively, when theelastomer is a fluoroelastomer and 80-98:1-20:0.2-5.0, respectively,when the elastomer is an ethylene alpha-olefin elastomer or an EPDMelastomer.

[0112] In order to optimize the elastomeric properties of seals made bythe above-described processes, they must be crosslinked, i.e. cured. Itwould be impractical to utilize a heat-activated cure system toaccomplish a rapid crosslinking reaction in such processes. One wouldrisk converting the curable composition used to form the seals to anintractable, crosslinked material during the metering step.Specifically, as the curable composition was heated or subjected totemperature elevation caused by mechanical working, the crosslinkingreaction would be triggered. It would be difficult to control prematuregelling (i.e. scorch) during metering. Because crosslinked compositionsdo not flow readily, processes which result in scorchy products areundesirable. Consequently, heterolytic cure systems, which rely onthermally-induced crosslinking reactions, are not appropriate for thepresent process. In addition, the most common homolytic, i.e. freeradical, curing processes, which depend on thermal decomposition ofperoxides, are also unsuitable for use in the present process. It has,however, been found that curable composition using the process of theinvention can be effectively cured by UV induced free radical processes.

[0113] UV cure of elastomeric compositions using the process of theinvention may be accomplished at room temperature or at highertemperatures. For example, in certain circumstances wherein theelastomeric composition is to be used as a sealant, it may be desirableto perform a photocure immediately after application of the uncuredcomposition to the object to be sealed. At that point, the temperatureof the composition may be as high as 250° C. However, heating thecurable composition is neither necessary nor particularly desirable foran effective photocure. In addition, when the compositions are used toform seals by the gasketing in place technique on thermoplasticarticles, low temperature cure minimizes any possibility of degradationor thermal distortion of the thermoplastic. Further, it is not necessaryto perform the UV irradiation in an inert atmosphere. The cure reactioncan be conducted under atmospheric conditions with no deleteriouseffects. In addition, it has also been found that in some cases,particularly when curing chlorinated or chlorosulfonated polyolefins,curing the composition under water is preferable to minimize heatbuildup. This minimizes the tendency of these polymers todehydrochlorinate, a process that causes polymer degradation anddiscoloration and which inhibits UV cure.

[0114] For purposes of the process of this invention, the wavelengthspectrum of radiation used to effect the curing reaction typicallycorresponds to the absorption maximum of the UV initiator. Thistypically ranges from about 200-400 nanometers. Suitable UV radiationsources include medium pressure mercury vapor lamps, electrodelesslamps, pulsed xenon lamps, and hybrid xenon/mercury vapor lamps. Apreferred arrangement comprises one or more lamps together with areflector, which diffuses the radiation evenly over the surface to beirradiated. The radiation dosage must be sufficient to cure thepolymeric composition, i.e. to produce a cured composition having acompression set of 90 or lower, preferably 50 or lower, and anelongation at break of at least 100%. A dosage of at least about 10joules per square centimeter, and preferably 20 joules is usuallysufficient for optimum cure. Dosage is a function of the time ofexposure to the UV radiation, the distance from the UV radiation sourceand the power level of the radiation source. The required radiation dosecan be readily determined by curing small samples of the curablecomposition and measuring physical properties, such as tensile strength,compression set and elongation, after cure. In most instances, anacceptable degree of cure can be obtained by exposures of 30-300 secondsusing a lampt of about 80 W/cm. Appropriate adjustments may be madedepending on the power of the lamp, distribution of the output over theUV range, the thickness of the sample as well as the polymericcomponent, level of crosslinking agent present, and level of fillerpresent. For example, ethylene acrylate copolymer rubber containingfiller would require a longer cure time than the same compositionwithout filler.

[0115] Foaming agents may be incorporated into the curable compositionsof the present invention. In such circumstances a cellular structurewill be formed by exposure of the curable composition to UV radiation asa result of thermal decomposition of the foaming agent induced bysimultaneous heating that occurs during exposure to UV light. Thisheating phenomenon may be augmented and controlled by additionalexternal application of heat. Typical foaming agents that may beemployed include p,p′-oxybisbenzenesulfonyl hydrazide,azodicarbon-amides, p-toluenesulfonyl semicarbazides, anddinitrosopentamethylene tetramine. Alternatively, the UV curing reactionmay also be accomplished with cooling, so that curing and foaming occursequentially, rather than simultaneously. That is, the curablecomposition is exposed to UV radiation with cooling, and the curedcomposition is then passed through a hot air tunnel to cause foaming.Closed cell structures of low specific gravity may be prepared by suchprocesses. For example, structures with specific gravities of 0.3 g/cm³may be obtained.

[0116] Low viscosity compositions of the invention may be utilized ascoating compositions for solvent-free systems or systems having lowlevels, i.e. up to about 2 wt. % of solvent, based on the total weightof elastomer, multifunctional crosslinker and UV initiator. It is thusnot necessary to cast films from polymer solutions. Instead, the lowviscosity curable composition flows onto the substrate by application ofheat. The optimum ratio of elastomer, multifunctional crosslinking agentand UV initiator for coating compositions will be different from that ofcompositions useful in the manufacture of seals and gaskets. Forexample, a relatively thin coating will cure more quickly and permit useof relatviely high levels of UV initiator because opacity will not be aproblme. In addition, higher levels of multifunctional crosslinkingagents may be employed to reduce viscosity and permit easier processingbecause coating compositions can tolerate higher hardness than gasketingmaterials. Further, coating compositions do not require the compressionset resistance that is necessary for seals and gaskets.

[0117] The curable elastomeric compositions of the present invention areuseful in manufacture of general rubber goods, coating compositions,foams and wire coating. They are most advantageously used however, inpreparation of seals and gaskets for thermoplastic articles,particularly those employed in automotive applications.

[0118] The invention is illustrated by the following specificembodiments wherein all parts are by weight unless otherwise indicated.

EXAMPLES Example 1

[0119] A curable elastomeric composition of the invention was preparedby mixing on a rubber mill 92.5 parts of a copolymer of ethylene andmethyl acrylate (ethylene content 34 wt. %, Mooney viscosity ML1+4 (100°C.) of 8), 7.5 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α,-dimethylbenzyl)diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 6 mm thickness were shaped by molding in a moldcoated with Teflon®fluoropolymer resin. The slabs were exposed for oneand two minutes respectively to UV radiation from a medium pressuremercury lamp which emitted radiation of wavelength approximately 250-400nm at 80 watts/cm. The distance of the samples from the lamp was 10 cm.The cured samples exhibited the properties shown in Table I. TABLE ILength of Exposure (Minutes) 1 2 Hardness, Shore A 46 50 Surface FacingSource Hardness, Shore A 35 42 Surface Away From Source

Example 2

[0120] A curable elastomeric composition of the invention was preparedby mixing on a rubber mill 92.5 parts of an acrylate rubber (ethylacrylate homopolymer, Mooney viscosity ML1+4 (100° C.) of 36, availablefrom Nippon Zeon KK), 7.5 parts trimethylolpropane triacrylate, 0.75parts Irgacure®1800 photoinitiator (a mixture of 75 wt. %1-hydroxycyclohexyl phenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)-diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 6 mm thickness were shaped by molding in a moldcoated with Teflon®fluoropolymer resin. The slabs were exposed for oneand two minutes respectively to UV radiation from a medium pressuremercury lamp which emitted radiation of wavelength approximately 250-400nm at 80 watts/cm. Cure was effected on samples placed 10 cm from thelamp. The cured samples exhibited the properties shown in Table II.TABLE II Length of Exposure (Minutes) 1 2 Hardness, Shore A 34 45Surface Facing Source Hardness, Shore A 25 30 Surface Away From Source

Example 3

[0121] A curable elastomeric composition of the invention was preparedby mixing on a rubber mill 92.5 parts of a copolymer of ethylene andvinyl acetate (ethylene content 32 wt. %, Mooney viscosity ML1+4 (100°C.) of 9), 7.5 parts trimethylolpropane triacrylate, 0.75 partsIrgacure®1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 partsantioxidant (4,4′-di(α, α-dimethylbenzyl)diphenylamine, available fromUniroyal, Inc.). Uncured slabs of 6 mm thickness were shaped by moldingin a mold coated with Teflon®fluoropolymer resin. Samples of the rubbersheet were exposed for two minutes respectively to UV radiation from amedium pressure mercury lamp, which emitted radiation of from about 250nm to 400 nm at 80 watts/cm. The distance of the samples from the lampduring the curing process was 10 cm. The cured samples exhibited theproperties shown in Table III. TABLE III Length of Exposure (Minutes) 2Hardness, Shore A 45 Surface Facing Source Hardness, Shore A 36 SurfaceAway From Source

Example 4

[0122] Three curable compositions of the present invention, Samples 4A,4B, and 4C, were prepared by mixing on a rubber mill 85 parts of acopolymer of ethylene and methyl acrylate (ethylene content 34 wt. %,Mooney viscosity ML1+4 (100° C.) of 8) and the components shown in TableIV. Uncured slabs of 6 mm thickness were shaped by molding in a moldcoated with Teflon®fluoropolymer resin. The resultant polymer slabs wereexposed for 4 minutes to UV radiation from a medium pressure mercurylamp, which emitted radiation of wavelength approximately 300-400 nm ata power of 80 W/cm. Exposure of the samples was at a distance of 10 cmfrom the lamp. Shore A hardness of the surface exposed to the lamp andthe surface facing away from the lamp were determined for the 6 mmspecimens. In addition, compression set of the cured compositions wasdetermined according to ISO 815 on specimens died out of the 6 mm slabs.Results are shown in Table IV. TABLE IV 4A 4B 4C Sample CompositionPolymer (parts) 85 85 85 Trimethylolpropane triacrylate 15 — —Trimethylolpropane trimethacrylate — 15 — Diethyleneglycoldimethacrylate — — 15 Naugard 445 ® Antioxidant 0.5 0.5 0.5 Irgacure ®1800 Photoinitiator 1 1 1 Physical Properties Hardness, Shore A (pts) 6968 65 Surface Exposed to Radiation Hardness, Shore A (pts) 61 59 55Surface Away from Source Compression Set (%) 25 30 90 22 hours @ 150°C., 25% deflection

Example 5 and Comparative Example A

[0123] Three curable compositions of the present invention, Samples 5A,5B, and 5C, were prepared by mixing on a rubber mill of a copolymer ofethylene and methyl acrylate (ethylene content 34 wt. %, Mooneyviscosity ML1+4 (100° C.) of 8) and the components shown in Table V.Uncured slabs of 6 mm thickness were shaped by molding in a mold coatedwith Teflon®fluoropolymer resin. The resultant polymers were exposed for2 minutes to UV radiation from a medium pressure mercury lamp, whichemitted radiation of wavelength approximately 250-400 nm at a power of80 W/cm. The distance of the samples from the lamp during the curingprocess was 10 cm. Shore A hardness of the surface of the 6 mm slabsexposed to the lamp and the surface facing away from the lamp weredetermined. In addition, compression set of the cured compositions wasdetermined according to ISO 815 on specimens died out of the 6 mm slabs.Tensile strength, modulus, and elongation at break were determinedaccording to ISO 37 T2 on 2 mm specimens. Results are shown in Table V.For purposes of comparison, a composition was prepared which contained aperoxide cure system. This composition was also prepared in the samemanner as Samples 5A-5C. The components of the composition, labeledSample A, are shown in Table V. Sample A was press cured at 180° C. for4 minutes and physical properties of the cured composition weredetermined in the same manner as those of Samples 5A-5C. Compressionmolding of the control sample resulted in formation of blisters in thespecimen and the physical properties of the sample were thereforedifficult to determine. TABLE V 5A 5B 5C A Sample Composition¹ Polymer88 92.5 95 100 Trimethylolpropane triacrylate 10 7.5 5 — Irgacure 1800Photoinitiator 0.75 0.75 0.75 — N,N′-m-Phenylenedimaleimide — — — 2Peroxide² — — — 5 Naugard ® 445 Antioxidant 0.5 0.5 0.5 0.5 PhysicalProperties Time of Exposure to UV Light 2 2 2 — (Minutes) Press Cure @160° C. — — — 30 (Minutes) Hardness, Shore A (pts) 59 50 42 30 SurfaceExposed to Radiation Hardness, Shore A (pts) 56 42 38 — Surface AwayFrom Source T_(B) (MPa)³ 4.7 3.8 2.7 1.1 M₁₀₀ (MPa)⁴ 2.2 1.2 0.6 0.5M₂₀₀ (MPa)⁵ 4.1 2.6 0.9 0.8 E_(B) (%)⁶ 250 317 450 250 Compression Set(%) 25 33 38 85 168 hours, 150° C., 25% deflection

Example 6

[0124] A curable elastomeric composition of the invention, Sample 6, wasprepared by mixing on a rubber mill 88 parts of a copolymer of ethyleneand methyl acrylate (ethylene content 34 wt. %, Mooney viscosity ML1+4(100° C.) of 8), 12 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)-diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 6 mm thickness and 2 mm thickness were shaped bymolding in a mold coated with Teflon®fluoropolymer resin. Samples ofboth the 2 mm thick slabs and the 6 mm thick slabs were exposed for 240seconds to UV radiation from a medium pressure mercury lamp, whichemitted radiation of wavelength approximately 300-400 nm at 80 watts/cm.The distance of the samples from the lamp during the curing process was10 cm. The cured samples exhibited the hardness and compression setproperties shown in Table VI. Test specimens of the cured compositionwere died out of the 6 mm slabs and used for compression set testing.Samples for tensile, modulus, and elongation testing were died out ofthe 2 mm slabs. Physical properties are shown in Table VI. TABLE VISample 6 Composition (phr) Polymer 88 Naugard ® 445 Antioxidant 0.5Trimethylolpropane triacrylate 12 Irgacure ® 1800 photoinitiator 0.75Hardness, Shore A (6 mm thick specimens) Surface Exposed to Radiation(pts) 63 Surface Away from Source (pts) 56 Compression Set (%) 25%deflection After 170 hours in air at 150° C. 24 After 500 hours in airat 150° C. 35 After 1000 hours in air at 150° C. 48 After 170 hours inengine oil at 150° C. 11 After 500 hours in engine oil at 150° C. 24After 1000 hours in engine oil at 150° C. 45 Physical Properties (2 mmthick specimens, room temperature) T_(B) (MPa) 7.9 M₁₀₀ (MPa) 4.0 E_(B)(%) 366 Hardness, Shore A (pts) 60 Physical Properties (2 mm thickspecimens, aged at 150° C. for 1000 hours in air) T_(B) (MPa) 7.2 M₁₀₀(MPa) 4.3 E_(B) (%) 337 Hardness, Shore A (pts) 63 Physical Properties(2 mm thick specimens, aged at 150° C. for 1000 hours in engine oil¹)T_(B), (MPa) 7.3 M₁₀₀ (MPa) 4.9 E_(B) (%) 196 Hardness, Shore A (pts) 57

Example 7

[0125] A curable elastomeric composition of the invention, Sample 7, wasprepared by mixing on a rubber mill 88 parts of a copolymer of ethyleneand methyl acrylate (ethylene content 34 wt. %, Mooney viscosity ML1+4(100° C.) of 8), 12 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)-diphenylamine, available from Uniroyal,Inc.). The composition was introduced to a 20 liter steel drum melter.The piston, which was maintained at a temperature of 140° C., heated andsoftened the composition while delivering it, at a pressure of 3.5 bars,to a gear pump which continuously fed a stream to a volumetricapplication gun mounted on an industrial robot. The composition wasapplied during a period of less than 15 seconds to the groove of athermoplastic automobile engine cover. The groove had a total length ofapproximately 1.2 m. The cover was conveyed under a medium pressuremercury lamp having wavelength approximately 250-400 nm and a powerrating of 100 W/cm. The lamp was approximately 15 cm from the surface ofthe curable composition. Exposure was for approximately 40 seconds. Thecomposition was sufficiently cured to exhibit a Shore A hardness of55-60.

Example 8

[0126] A curable elastomeric composition of the invention was preparedby mixing on a rubber mill 92.5 parts of a copolymer of butadiene andacrylonitrile (acrylonitrile content 41 wt. %; Mooney viscosity ML 1+4(100° C.) of 80), 7.5 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 2 mm and 6 mm thickness were shaped by moldingin a mold coated with Teflon®fluoropolymer resin. The resultant 2 mm and6 mm slabs were exposed for two minutes to UV radiation from a mediumpressure mercury lamp (80 W/cm) that emitted radiation of wavelengthapproximately 250-400 nm at a distance of 10 cm from the lamp. Shore Ahardness of the surface exposed to the lamp and the surface facing awayfrom the lamp of the 6 mm slabs were determined. Tensile strength,modulus, and elongation at break of the cured compositions died from the2 mm slab were determined according to ISO 37 T2. Results are shown inTable VII. TABLE VII Sample 8 Composition (phr) Polymer 92.5 Naugard ®445 Antioxidant 0.5 Trimethylolpropane triacrylate 7.5 Irgacure ® 1800photoinitiator 0.75 Hardness, Shore A (6 mm thick specimens) SurfaceExposed to Radiation 49 Surface Away from Source (pts) 39 PhysicalProperties (2 mm thick specimens) T_(B) (MPa) 1.7 M₁₀₀ (MPa) 1.1 E_(B)(%) 174

Example 9

[0127] A curable elastomeric composition of the invention was preparedby mixing on a rubber mill 92.5 parts of a hydrogenated copolymer ofbutadiene and acrylonitrile (acrylonitrile content 33.5 wt. %; Mooneyviscosity ML 1+4 (100° C.) of 70; double bond content less than 1%), 7.5parts trimethylolpropane triacrylate, 0.75 parts Irgacure® 1800photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexyl phenyl ketoneand 25 wt. % bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphineoxide, available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445antioxidant (4,4′-di(α, α-dimethylbenzyl)diphenylamine, available fromUniroyal, Inc.). Uncured slabs of 2 mm and 6 mm thickness were shaped bymolding in a mold coated with Teflon®fluoropolymer resin. The resultant2 mm and 6 mm slabs were exposed for two minutes to UV radiation from amedium pressure mercury lamp which emitted radiation of wavelengthapproximately 250-400 nm at a distance of 10 cm from the lamp. Shore Ahardness of the surface exposed to the lamp and the surface facing awayfrom the lamp of the 6 mm slabs were determined. Tensile strength,modulus, and elongation at break of the cured compositions died from the2 mm slab were determined according to ISO 37 T2. Results are shown inTable VIII. TABLE VIII Sample 9 Composition (phr) Polymer 92.5 Naugard ®445 Antioxidant 0.5 Trimethylolpropane triacrylate 7.5 Irgacure ® 1800photoinitiator 0.75 Hardness, Shore A (6 mm thick specimens) SurfaceExposed to Radiation 53 Surface Away from Source (pts) 39 PhysicalProperties (2 mm thick specimens) T_(B) (MPa) 5.8 M₁₀₀ (MPa) 1.2 E_(B)(%) 516

Example 10

[0128] A curable elastomeric composition of the invention was preparedby mixing on a rubber mill 92.5 parts of Therban®XN 535C (a hydrogenatedterpolymer of butadiene, acrylonitrile, and a termonomer, available fromBayer AG), 7.5 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 2 mm and 6 mm thickness were shaped by moldingin a mold coated with Teflon®fluoropolymer resin. The resultant 2 mm and6 mm slabs were exposed for two minutes to UV radiation from a mediumpressure mercury lamp (80 W/cm) that emitted radiation of wavelengthapproximately 250-400 nm at a distance of 10 cm from the lamp. Shore Ahardness of the surface exposed to the lamp and the surface facing awayfrom the lamp of the 6 mm slabs were determined. Tensile strength,modulus, and elongation at break of the cured compositions died from the2 mm slab were determined according to ISO 37 T2. Results are shown inTable IX. TABLE IX Sample 10 Composition (phr) Polymer 92.5 Naugard ®445 Antioxidant 0.5 Trimethylolpropane triacrylate 7.5 Irgacure ® 1800photoinitiator 0.75 Hardness, Shore A (6 mm thick specimens) SurfaceExposed to Radiation 42 Surface Away from Source (pts) 36 PhysicalProperties (2 mm thick specimens) T_(B) (MPa) 4.6 M₁₀₀ (MPa) 1.1 E_(B)(%) 351

Example 11

[0129] A curable elastomeric composition of the invention, Sample 11A,was prepared by mixing on a rubber mill 92.5 parts of a copolymer ofethylene and methyl acrylate (ethylene content 34 wt. %, Mooneyviscosity ML(1+4 @ 100° C. of 8), 7.5 parts pentaerythritoltetraacrylate (Sartomer 295, available from Sartomer, Inc.), 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. %1-hydroxy-cyclohexyl phenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard®445 antioxidant(4,4′-di((α, α-dimethylbenzyl)diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 6 mm thickness and 2 mm thickness were shaped bymolding in a mold coated with Teflon™fluoropolymer resin. Samples of the2 mm thick slabs thick slabs were exposed for 120 seconds to UVradiation from a medium pressure mercury lamp (80 W/cm), which emittedradiation of wavelength greater than 250 nm. Samples of the 6 mm thickslabs thick slabs were similarly exposed for 240 seconds. The distanceof the samples from the lamp during the curing process was 10 cm. Thecured samples exhibited the hardness and compression set propertiesshown in Table X. Test specimens of the cured composition were died outof the 6 mm slabs and used for compression set testing. Samples fortensile, modulus, and elongation testing were died out of the 2 mmslabs. Physical properties are shown in Table X. Samples 11B, C, and Dwere similarly prepared using the ingredients shown in Table X. Testresults for Samples are 11B-D are also shown in Table X. TABLE X 11A 11B11C 11D Composition (phr) Polymer 92.5 92.5 92.5 92.5 PentaerythritolTetraacrylate¹ 7.5 5 0 0 Pentaerythritol Pentaacrylate² 0 0 7.5 5Naugard ® 445 Antioxidant 0.5 0.5 0.5 0.5 Irgacure ® 1800 Photoinitiator0.75 0.75 0.75 0.75 Hardness, Shore A (6 mm thick specimens) Surfaceexposed to radiation (pts) 52 39 52 44 Surface away from source (pts) 4537 46 39 Compression Set (%) 30 39 32 39 168 hours @ 150° C. in airPhysical Properties (2 mm thick specimens)³ M₁₀₀ (MPa) 1.6 0.6 1.7 0.8T_(B) (MPa) 4.3 2.7 3.9 3.3 E_(B) (%) 236 383 200 332 Hardness, Shore ASurface 50 40 50 43 exposed to radiation (pts)

Example 12

[0130] A curable elastomeric composition of the invention, Sample 12A,was prepared by mixing on a rubber mill 92.5 parts of Therban® A 4307Rubber (a hydrogenated copolymer of butadiene and acrylonitrile,available from Bayer AG), 7.5 parts trimethylolpropane triacrylate, 0.75parts Irgacure® 1800 photoinitiator (a mixture of 75 wt. %1-hydroxycyclohexyl phenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), and 0.5 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)-diphenylamine, available from Uniroyal,Inc.). Uncured slabs of 2 mm thickness were shaped by molding in a moldcoated with Teflon®fluoropolymer resin. The resultant 2 mm slabs wereexposed for four minutes to UV radiation from a medium pressure mercurylamp (80 W/cm) which emitted radiation of wavelength greater than 250 nmat a distance of 10 cm from the lamp. Shore A hardness, tensilestrength, modulus, and elongation at break of the cured compositionsdied from the 2 mm slab were determined according to ISO 37 T2 at roomtemperature. Results are shown in Table XI. Two further compositions ofthe invention, Samples 12B and 12C, were prepared in a similar fashionusing the proportion of components shown in Table XI. Test specimenswere prepared as described for Sample 12 A and results are shown inTable XI. TABLE XI Sample Sample Sample 12A 12B 12C Composition (phr)Polymer 92.5 92.5 92.5 Naugard ® 445 Antioxidant 0.5 0.5 0.5Trimethylolpropane triacrylate 7.5 7.5 7.5 Irgacure ® 1800photoinitiator 0.75 1.2 2 Physical Properties (2 mm thick specimens)T_(B) (MPa) 8.5 6.5 7 M₁₀₀ (MPa) 1.5 1.2 1.3 E_(B) (%) 490 420 420Hardness Shore A 58 58 58 Surface exposed to radiation (pts) CompressionSet (%) 75 62 58 168 hours @ 150° C. in air

Example 13

[0131] A curable elastomeric composition of the invention, Sample 13,was prepared substantially in the same manner and using the samecomponents as Sample 12B except that 92.5 parts of Therban® Rubber A4367 (a hydrogenated copolymer of butadiene and acrylonitrile, availablefrom Bayer AG; acrylonitrile content 43 wt. %; Mooney viscosity ML 1+4(100° C.) of 70; double bond content 5.5%), was used in place ofTherban® A 4307 as the polymer component. Uncured slabs of 2 mmthickness were shaped by molding in a mold coated withTeflon®fluoropolymer resin. The resultant 2 mm slabs were exposed forfour minutes to UV radiation from a medium pressure mercury lamp (80W/cm) that emitted radiation of wavelength greater than 250 nm at adistance of 10 cm from the lamp. Tensile strength, modulus, andelongation at break of the cured compositions died from the 2 mm slabwere determined according to ISO 37 T2 at room temperature. Results areshown in Table XII. Test specimens were prepared as described for Sample12 A and results are shown in Table XII. TABLE XII Sample Sample 12B 13Composition (phr) Therban ® A 4307 Rubber 92.5 0 Therban ® A 4367 Rubber0 92.5 Naugard ® 445 Antioxidant 0.5 0.5 Trimethylolpropane triacrylate7.5 7.5 Irgacure ® 1800 photoinitiator 1.2 1.2 Physical Properties (2 mmthick specimens) T_(B) (MPa) 6.5 5.7 M₁₀₀ (MPa) 1.2 1.6 E_(B) (%) 420320 Hardness Shore A 58 59 Surface exposed to radiation (pts)Compression Set (%) 62 53 168 hours @ 150° C.in air

Example 14

[0132] A curable elastomeric composition of the invention, Sample 14A,was prepared by mixing on a rubber mill 92.5 parts of Elvaloy®742 resinmodifier (a copolymer of ethylene, vinyl acetate and carbon monoxidecontaining 28.5 wt. % vinyl acetate units, and 9 wt. % carbon monoxideunits, having a melt index of 35 g/10 minutes, available from E. I. duPont de Nemours and Co.), 7.5 parts trimethylolpropane triacrylate, and0.75 parts Irgacure® 1800 photoinitiator (a mixture of 75 wt. %1-hydroxycyclohexyl phenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.) Uncured slabs of 2 mm thickness wereshaped by molding in a mold coated with Teflon®fluoropolymer resin. Theresultant 2 mm slabs were exposed for two minutes to UV radiation from amercury lamp (80 W/cm) that emitted radiation of wavelength greater than250 nm at a distance of 10 cm from the lamp. Shore A hardness of thesurface exposed to the lamp and the surface facing away from the lampwere determined. Tensile strength, modulus, and elongation at break ofthe cured compositions died from the 2 mm slab were determined accordingto ISO 37 T2. Results are shown in Table XIII. In addition, Samples 14Band 14C were prepared and tested in a similar manner. Sample 14Bcontained Elvaloy®HP 661 resin modifier (a copolymer of ethylene, butylacrylate and carbon monoxide containing 29 wt. % butyl acrylate units,and 10 wt. % carbon monoxide units, having a melt index of 12 g/10minutes, available from E. I. du Pont de Nemours and Co.) as thepolymeric component. Sample 14C contained Elvaloy®AS resin modifier (acopolymer of ethylene, n-butyl acrylate and glycidyl methacrylatecontaining 28 wt. % n-butyl acrylate units, and 5.25 wt. % glycidylmethacrylate units, having a melt index of 12 g/10 minutes, availablefrom E. I. du Pont de Nemours and Co.) as the polymeric component.Physical test results are shown in Table XIII. TABLE XIII 14A 14B 14CComposition Elvaloy ® 742 resin modifier 92.5 0 0 Elvaloy ® HP 661 resinmodifier 0 92.5 0 Elvaloy ® AS resin modifier 0 0 92.5Trimethylolpropane triacrylate 7.5 7.5 7.5 Irgacure ® 1800photoinitiator 0.75 0.75 0.75 Hardness, Shore A (2 mm thick specimens)Uncured Hardness (points) 58 64 65 Surface Exposed to Radiation (points)68 68 72 Surface Away from Source (points) 66 67 71 Physical Properties(2 mm thick specimens) T_(B) (MPa) 9.6 7.8 9.9 M₁₀₀ (MPa) 3.9 3.1 3.1E_(B) (%) 350 420 600 Compression Set, (%), 70 hours @ 125° C. 42 28 32

Example 15

[0133] A curable elastomeric composition of the invention was preparedby mixing on a rubber mill 90.3 parts of a copolymer of ethylene andmethyl acrylate (ethylene content 34 wt. %, Mooney viscosity ML 1+4(100° C.) of 8), 8.46 parts trimethylolpropane triacrylate, 0.75 partsIrgacure® 1800 photoinitiator (a mixture of 75 wt. % 1-hydroxycyclohexylphenyl ketone and 25 wt. %bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide,available from Ciba-Geigy, Ltd.), 0.49 parts Naugard® 445 antioxidant(4,4′-di(α, α-dimethylbenzyl)-diphenylamine, available from Uniroyal,Inc.), and 5 parts of Celogen®OT blowing agent[p,p′-oxybis(benzenesulfonyl hydrazide), available from Uniroyal, Inc.].Uncured slabs of 2 mm thickness were shaped by molding in a mold coatedwith Teflon®fluoropolymer resin. The slabs were exposed for 4 minutes toUV radiation from a medium pressure mercury lamp (80 W/cm) that emittedradiation of wavelength greater than 250 nm. The distance of the samplesfrom the lamp was 10-15 cm. The temperature of the cured samples at theconclusion of UV exposure was 140°-150° C. A foam having a closed cellstructure with integral skin was formed having specific gravity down to0.3 g/cm.

Example 16

[0134] A curable elastomeric composition of the invention, Sample 16A,was prepared by mixing the following components on a rubber mill: 94parts of a copolymer of vinylidene fluoride (VF₂), perfluoromethylperfluorovinyl ether (PMVE), tetrafluoroethylene (TFE), and4-bromo-3,3,4,4-tetrafluorobutene-1(BTFB) (weight ratioVF₂:TFE:PMVE:BTFB 54:10:35:1.2), 6.0 parts trimethylolpropanetriacrylate, and 0.5 parts Irgacure 1800® photoinitiator. The milledcomposition was shaped into uncured slabs of 2 mm thickness were shapedby molding in a mold coated with Teflon®fluoropolymer resin. An uncuredslab was exposed for one minute to UV radiation from a medium pressuremercury lamp that emitted radiation of wavelength approximately 250-400nm at 80 watts/cm. The distance of the samples from the lamp was 10 cm.The cured samples exhibited the properties shown in Table XIV. Twoadditional samples, 16B and 16C, were prepared in substantially the samemanner except that Sample 16B contained 8 parts of trimethylolpropanetriacrylate and Sample 16C contained 0.5 parts tri-n-butyltin hydride inaddition to the 6 parts of trimethylolpropane triacrylate. Samples 16Band 16C were cured substantially in the same manner as Sample 16A.Physical properties of the cured slabs are shown in Table XIV. TABLE XIV16A 16B 16C Sample Composition Polymer 94 92 94 Trimethylolpropanetriacrylate 6 8 6 Irgacure ® 1800 Photoinitiator 0.5 0.5 0.5Tri-n-butyltin hydride — — 0.5 Physical Properties Hardness, Shore A(pts) 59 70 — Surface Exposed to Radiation Hardness, Shore A (pts)Surface Away From Source T_(B) (MPa) 9.1 10.9 13.8 M₁₀₀ (MPa) 3.1 5.4 7E_(B) (%) 450 339 273 Compression Set (%) 69 — 36 22 hours, 150° C., 25%deflection, 2 minute UV exposure

Example 17

[0135] A curable elastomeric composition of the invention, Sample 17A,was prepared by mixing the following components on a rubber mill: 94parts of an iodinated copolymer VF₂, PMVE, TFE, and BTFB (weight ratioVF₂:TFE:PMVE:BTFB 54:10:35:0.6; prepared in the presence of an iodinatedchain transfer agent and having an iodine content of 0.18), 6.0 partstrimethylolpropane triacrylate, and 1 part Irgacure 1800®photoinitiator. The milled composition was shaped, into uncured slabs of2 mm thickness were shaped by molding in a mold coated with Teflon®fluoropolymer resin. An uncured slab was exposed for one minute to UVradiation from a medium pressure mercury lamp which emitted radiation ofwavelength approximately 250-400 nm at 80 watts/cm. The distance of thesamples from the lamp was 10 cm. The cured samples exhibited theproperties shown in Table XV. Three additional samples, 17B, 17C, and17D, were prepared in substantially the same manner except that eachcontained 0.5 parts of Irgacure 1800, Sample 17B contained 94 parts ofan iodine-free copolymer of VF₂, PMVE, TFE, and BTFB having a monomerratio of 54:10:35:1.2; Sample 17C contained 94 parts of an iodine-freecopolymer of VF₂, PMVE, TFE, and BTFB having a monomer ratio of52.9:10.2:34.9:2.2; and Sample 17D contained 94 parts of an iodine-freecopolymer of VF₂, PMVE, TFE, and BTFB having a monomer ratio of53.5:10:34.4:2.2. Samples 17B-17D were cured substantially in the samemanner as Sample 3A. Physical properties of the cured slabs are shown inTable XV. TABLE XV 17A 17B 17C 17D Sample Composition Polymer 94 94 9494 Trimethylolpropane triacrylate 6 6 6 6 Irgacure ® 1800 Photoinitiator1 0.5 0.5 0.5 Physical Properties Hardness, Shore A (pts) 49 59 60 —Surface Exposed to Radiation T_(B) (MPa) 2 9.1 7.5 9.9 M₁₀₀ (MPa) 1.43.1 3.3 3.8 E_(B) (%) 537 450 346 431 Compression Set (%) — 69 75.3 76.222 hours, 150° C., 25% deflection, 2 minute UV exposure

Example 18

[0136] A curable elastomeric composition of the invention, Sample 18A,was prepared by mixing the following components on a rubber mill: 92parts of a copolymer VF₂, PMVE, TFE, and BTFB (weight ratioVF₂:TFE:PMVE:BTFB 52.9:10.2:34.9:2.0), 8.0 parts trimethylolpropanetriacrylate, and 0.5 parts Irgacure 1800® photoinitiator. The milledcomposition was shaped into uncured slabs of_ mm thickness were shapedby molding in a mold coated with Teflon® fluoropolymer resin. An uncuredslab was exposed for one minute to UV radiation from a medium pressuremercury lamp which emitted radiation of wavelength approximately 250-400nm at 80 watts/cm. The distance of the samples from the lamp was 10 cm.The cured samples exhibited the properties shown in Table XVI. Anadditional sample, 18B, was prepared in substantially the same manner.However, Sample 18B contained 100 parts polymer and additionallycontained 0.5 parts tri-n-butyltin hydride. Sample 18B was curedsubstantially in the same manner as Sample 18A. Physical properties ofthe cured slabs are shown in Table XVI. TABLE XVI 18A 18B SampleComposition Polymer 92 100 Trimethylolpropane triacrylate 8 8 Irgacure ®1800 Photoinitiator 0.5 0.5 Tri-n-butyltin Hydride — 0.5 PhysicalProperties Hardness, Shore A (pts) — 68 Surface Exposed to RadiationT_(B) (MPa) 10 11.8 M₁₀₀ (MPa) 6 6.3 E_(B) (%) 284 239 Compression Set(%) 74.4 35.4 22 hours, 120 C., 25% deflection, 2 minute UV exposure

Example 19

[0137] A curable elastomeric composition of the invention, Sample 19A,was prepared by mixing the following components on a rubber mill: 92parts of a copolymer VF₂, PMVE, TFE, and BTFB (weight ratioVF₂:TFE:PMVE:BTFB 53.5:10:34.4:2.2), 8.0 parts trimethylolpropanetriacrylate, and 0.5 parts Irgacure 1800® photoinitiator. The milledcomposition was shaped into uncured slabs of 2 mm thickness were shapedby molding in a mold coated with Teflon®fluoropolymer resin. An uncuredslab was exposed for one minute to UV radiation from a medium pressuremercury lamp which emitted radiation of wavelength approximately 250-400nm at 80 watts/cm. The distance of the samples from the lamp was 10 cm.The cured samples exhibited the properties shown in Table XVII. Anadditional sample, 19B, was prepared in substantially the same manner.However, Sample 19B contained 100 parts polymer, 1 part Irgacure 1800®photoinitiator and additionally contained 1 part tri-n-butyltin hydride.Sample 19B was cured substantially in the same manner as Sample 19A.Physical properties of the cured slabs are shown in Table XVII. TABLEXVII 19A 19B Sample Composition Polymer 92 100 Trimethylolpropanetriacrylate 8 8 Irgacure ® 1800 Photoinitiator 0.5 1.0 Tri-n-butyltinHydride — 0.5 Physical Properties Hardness, Shore A (pts) 61 71 SurfaceExposed to Radiation T_(B) (MPa) 9.9 11.8 M₁₀₀ (MPa) 5.7 7.3 E_(B) (%)356 215 Compression Set (%) 71.5 43.3 22 hours, 150° C., 25% deflection,2 minute UV exposure

Example 20

[0138] A curable elastomeric composition of the invention, Sample 20,was prepared by mixing the following components on a rubber mill: 90parts of a chlorosulfonated polyethylene elastomer [chlorine content 29wt. %, sulfur content of 1.4 wt. % and a Mooney viscosity, ML 1+4 (100°C.) of 22], 10.0 parts trimethylolpropane triacrylate, and 0.5 partsIrgacure®184 photoinitiator (1-hydroxycyclohexyl phenyl ketone,available from Ciba Geigy, Inc.). The milled composition was shaped intouncured slabs of 2 mm thickness for tensile testing specimens and 6 mmthickness for cutting compression set disks. The slabs were shaped bymolding in a mold coated with Teflon®fluoropolymer resin. The uncuredslabs were exposed to UV radiation from a medium pressure mercury lampwhich emitted radiation of wavelength approximately 250-400 nm at 80watts/cm. The 2 mm slabs were exposed for 4 minutes and the 6 mm slabswere exposed for 6 minutes. Exposure was effected under water to limitthe heat build-up in the elastomeric composition which could causeexcessive dehydrochlorination and polymer degradation. The distance ofthe samples from the lamp was 10 cm. The cured samples exhibited theproperties shown in Table XVIII. TABLE XVIII 20 Sample CompositionPolymer 90 Trimethylolpropane triacrylate 10 Irgacure ® 184Photoinitiator 0.5 Physical Properties Hardness,¹ Shore A (pts) 63Surface Exposed to Radiation Hardness,¹ Shore A (pts) 61 Surface AwayFrom Source T_(B) (MPa) 4.7 M₁₀₀ (MPa) 3.6 E_(B) (%) 128 Compression Set(%) 57 70 hours, 125° C., 25% deflection, 4 minute UV exposure

Example 21

[0139] A curable elastomeric composition of the invention, Sample 21,was prepared by mixing the following components on a rubber mill: 85parts of a chlorinated polyethylene elastomer [chlorine content 36 wt. %and a Mooney viscosity, ML 1+4 (121° C.) of 36], 15 partstrimethylolpropane triacrylate, 1 part Irgacure 1800® photoinitiator and0.5 parts Naugard® 445 antioxidant (4,4′-bis-(α,α-dimethylbenzyl)diphenylamine). The milled composition was shaped intouncured slabs of 2 mm thickness for preparation of tensile specimens and6 mm thickness for cutting compression set disks. The slabs were shapedby molding in a mold coated with Teflon®fluoropolymer resin. An uncuredslab was exposed for 4 minutes, under water, to limit the heat build-upin the elastomeric compositions, to UV radiation from a medium pressuremercury lamp which emitted radiation of wavelength approximately 250-400nm at 80 watts/cm. The distance of the samples from the lamp was 10 cm.The cured samples exhibited the properties shown in Table XIX. TABLE XIX21 Sample Composition Polymer 85 Trimethylolpropane triacrylate 15Irgacure ® 1800 Photoinitiator 1.0 Naugard ® 445 Antioxidant 0.5Physical Properties Hardness,¹ Shore A (pts) 94 Surface Exposed toRadiation Hardness,¹ Shore A (pts) 91 Surface Away From Source T_(B)(MPa) 10.9 E_(B) (%) 93 Compression Set (%) 58 70 hours, 125° C., 25%deflection, 4 minute UV exposure, 6 mm slab

Example 22

[0140] A curable elastomeric composition of the invention, Sample 22,was prepared by mixing the following components on a rubber mill: 90parts of Hydrin®C 2000L epichlorohydrin elastomer (anepichlorohydrin/ethylene oxide copolymer, chlorine content 26 wt. %,Mooney viscosity 65, available from Nippon Zeon, Inc.], 10.0 partstrimethylolpropane triacrylate, and 0.75 parts Irgacure 184®photoinitiator (1-hydroxycyclohexyl phenyl ketone, available from CibaGeigy, Inc.). The milled composition was shaped into uncured slabs of 2mm thickness for preparation of tensile specimens and 6 mm thickness forcutting compression set disks. The slabs were shaped by molding in amold coated with Teflon®fluoropolymer resin. An uncured slab was exposedfor 4 minutes in water to UV radiation from a medium pressure mercurylamp which emitted radiation of wavelength approximately 250-400 nm at80 watts/cm. The distance of the samples from the lamp was 10 cm. Thecured samples exhibited the properties shown in Table XX. TABLE XX 22Sample Composition Polymer 90 Trimethylolpropane triacrylate 10Irgacure ® 184 Photoinitiator 0.75 Physical Properties Hardness¹, ShoreA (pts) 54 Surface Exposed to Radiation Hardness¹, Shore A (pts) 50Surface Away From Source T_(B) (MPa) 4.6 M₁₀₀ (MPa) 3.3 E_(B) (%) 187Compression Set (%) 24 70 hours, 120° C., 25% deflection, 4 minute UVexposure

We claim:
 1. A thermally stable, curable elastomer compositioncomprising a) 75 to 95 weight percent of an elastomer selected from thegroup consisting of 1) copolymers comprising ethylene and a comonomerselected from the group consisting of C₁-C₈ alkyl esters of acrylicacid, C₁-C₈ alkyl esters of methacrylic acid, and vinyl esters of C₂-C₈carboxylic acids; 2) alkyl acrylate polymers selected from the groupconsisting of homopolymers of C₁-C₁₀ alkyl acrylates and copolymers ofC₁-C₁₀ alkyl acrylates with up to 40 weight percent monovinyl monomers;and 3) diene copolymers selected from the group consisting of copolymersof a diene and an unsaturated nitrile and hydrogenated copolymers of adiene and an unsaturated nitrile; b) 2 to 24 weight percent of amultifunctional crosslinking agent selected from the group consisting ofmultifunctional acrylic crosslinking agents, multifunctional methacryliccrosslinking agents, multifunctional cyanurate crosslinking agents, andmultifunctional isocyanurate crosslinking agents; and c) 0.2 to 5.0weight percent of a UV initiator wherein the weight percentages of eachof components a), b), and c) are based on the combined weight ofcomponents a), b), and c).
 2. The composition of claim 1 wherein theelastomer is a copolymer comprising ethylene and a comonomer selectedfrom the group consisting of C₁-C₈ alkyl esters of acrylic acid andvinyl esters of C₂-C₈ carboxylic acids.
 3. The composition of claim 2wherein the elastomer is a copolymer of ethylene and a C₁-C₈ alkyl esterof acrylic acid.
 4. The composition of claim 3 wherein the elastomer isa copolymer of ethylene and methyl acrylate.
 5. The composition of claim2 wherein the elastomer is a copolymer of ethylene and a vinyl ester ofa C₂-C₈ carboxylic acid.
 6. The composition of claim 5 wherein theelastomer is ethylene vinyl acetate.
 7. The composition of claim 1wherein the elastomer is a copolymer comprising a) ethylene; b) acomonomer selected from the group consisting of C₁-C₈ alkyl esters ofacrylic acid, C₁-C₈ alkyl esters of methacrylic acid, and vinyl estersof C₂-C₈ carboxylic acids; and c) a comonomer selected from the groupconsisting of carboxylic acids of 3-12 carbon atoms selected from thegroup consisting of alpha, beta-unsaturated monocarboxylic acids, alpha,beta-unsaturated dicarboxylic acids, and monoesters of alpha,beta-unsaturated dicarboxylic acids.
 8. The composition of claim 7wherein the comonomer of b) is selected from the group consisting ofC₁-C₈ alkyl esters of acrylic acid, and vinyl esters of C₂-C₈ carboxylicacids.
 9. The composition of claim 7 wherein component c) is a monoesterof an alpha, beta-unsaturated dicarboxylic acid.
 10. The composition ofclaim 1 wherein the elastomer is a homopolymer of a C₁-C₁₀ alkylacrylate.
 11. The composition of claim 1 wherein the elastomer is acopolymer of a C₁-C₁₀ alkyl acrylate with up to 40 weight percentmonovinyl monomer.
 12. The composition of claim 1 wherein the elastomeris a copolymer of a diene and an unsaturated nitrile.
 13. Thecomposition of claim 1 wherein the multifunctional crosslinking agent isa multifunctional acrylate.
 14. The composition of claim 1 wherein themultifunctional crosslinking agent is a multifunctional methacrylate.15. The composition of claim 1 wherein the UV initiator is a ketone. 16.A process for applying a seal to an article comprising the steps of A)blending at a temperature of between 25° C. and 250° C.: 1) 75 to 95weight percent of an elastomer selected from the group consisting of a)copolymers comprising ethylene and a comonomer selected from the groupconsisting of C₁-C₈ alkyl esters of acrylic acid, C₁-C₈ alkyl esters ofmethacrylic acid, and vinyl esters of C₂-C₈ carboxylic acids; b) alkylacrylate polymers selected from the group consisting of homopolymers ofC₁-C₁₀ alkyl acrylates and copolymers of C₁-C₁₀ alkyl acrylates with upto 40 weight percent monovinyl monomers; and c) diene copolymersselected from the group consisting of copolymers of a diene and anunsaturated nitrile and hydrogenated copolymers of a diene and anunsaturated nitrile; 2) 2 to 24 weight percent of a multifunctionalcrosslinking agent selected from the group consisting of multifunctionalacrylic crosslinking agents, multifunctional methacrylic crosslinkingagents, multifunctional cyanurate crosslinking agents, andmultifunctional isocyanurate crosslinking agents; and 3) 0.2 to 5.0weight percent of a UV initiator  wherein the weight percentages of eachof components 1), 2), and 3) are based on the combined weight ofcomponents 1), 2), and 3), to form a thermally stable, curable,extrudable mixture; B) depositing said extrudable mixture on saidarticle in the shape and thickness desired to form an uncured seal; andC) irradiating said uncured seal with UV radiation for a time sufficientto cure said seal.
 17. The process of claim 16 wherein the curablecomposition is heated to a temperature of 90-170° C. in step A).
 18. Theprocess of claim 16 wherein the article is made of a thermoplasticmaterial.
 19. The process of claim 16 wherein the elastomer is acopolymer comprising ethylene and a comonomer selected from the groupconsisting of C₁-C₈ alkyl esters of acrylic acid and vinyl esters ofC₂-C₈ carboxylic acids.
 20. The process of claim 19 wherein theelastomer is a copolymer of ethylene and a C₁-C₈ alkyl ester of acrylicacid.
 21. The process of claim 20 wherein the elastomer is a copolymerof ethylene and methyl acrylate.
 22. The process of claim 19 wherein theelastomer is ethylene vinyl acetate.
 23. The process of claim 16 whereinthe elastomer is a copolymer comprising a) ethylene; b) a comonomerselected from the group consisting of C₁-C₈ alkyl esters of acrylicacid, C₁-C₈ alkyl esters of methacrylic acid, and vinyl esters of C₂-C₈carboxylic acids; and c) a comonomer selected from the group consistingof carboxylic acids of 3-12 carbon atoms selected from the groupconsisting of alpha, beta-unsaturated monocarboxylic acids, alpha,beta-unsaturated dicarboxylic acids and monoesters of alpha,beta-unsaturated dicarboxylic acids.
 24. The process of claim 23 whereincomponent c) is a monoester of an alpha, beta-unsaturated dicarboxylicacid.
 25. The process of claim 16 wherein the elastomer is a homopolymerof a C₁-C₁₀ alky l acrylate.
 26. The process of claim 16 wherein theelastomer is a copolymer of a C₁-C₁₀ alkyl acrylate with up to 40 weightpercent monovinyl monomer.
 27. The process of claim 16 wherein theelastomer is a copolymer of a diene and an unsaturated nitrile.
 28. Theprocess of claim 16 wherein the multifunctional crosslinking agent is amultifunctional acrylate.
 29. The process of claim 16 wherein themultifunctional crosslinking agent is a multifunctional methacrylate.30. A cured article produced by the process of claim
 16. 31. Thecomposition of claim 1 additionally comprising a foaming agent.
 32. Acurable elastomer composition of claim 1 wherein the elastomer has aMooney viscosity of 1-20 ML 1+4 (100° C.).
 33. A thermally stable,curable elastomer composition comprising A) 70 to 99 weight percent of afluoroelastomer having at least one cure site selected from the groupconsisting of 1) copolymerized brominated olefins, chlorinated olefinsand iodinated olefins; 2) copolymerized brominated unsaturated ethers,chlorinated unsaturated ethers, and iodinated unsaturated ethers; 3)copolymerized non-conjugated dienes and trienes and 4) iodine atoms andbromine atoms and mixtures thereof that are present at terminalpositions of the fluoroelastomer chain; B) 0.5 to 20 weight percent of amultifunctional crosslinking agent selected from the group consisting ofmultifunctional acrylic crosslinking agents, multifunctional methacryliccrosslinking agents, multifunctional cyanurate crosslinking agents, andmultifunctional isocyanurate crosslinking agents; and C) 0.1 to 10weight percent of a UV initiator wherein the weight percentages of eachof components A), B), and C) are based on the combined weight ofcomponents A), B), and C).
 34. The composition of claim 33 wherein thefluoroelastomer is a copolymer comprising copolymerized units ofvinylidene fluoride.
 35. The composition of claim 33 wherein thefluoroelastomer is a copolymer comprising copolymerized units oftetrafluoroethylene.
 36. The composition of claim 33 wherein the curesite is selected from the group consisting of copolymerized brominatedolefins, chlorinated olefins and iodinated olefins.
 37. The compositionof claim 33 wherein at least one cure site is selected from the groupconsisting of copolymerized brominated unsaturated ethers, chlorinatedunsaturated ethers, and iodinated unsaturated ethers.
 38. Thecomposition of claim 33 wherein at least one cure site is selected fromthe group consisting of copolymerized non-conjugated dienes.
 39. Thecomposition of claim 33 wherein at least one cure site is selected fromthe group consisting of iodine atoms and bromine atoms and mixturesthereof that are present at terminal positions of the fluoroelastomerchain.
 40. The composition of claim 33 having a cure site that is abrominated olefin.
 41. The composition of claim 40 wherein the cure siteis 4-bromo-3,3,4,4-tetrafluorobutene-1.
 42. The composition of claim 33wherein the multifunctional crosslinking agent is a multifunctionalacrylate.
 43. The composition of claim 33 wherein the multifunctionalcrosslinking agent is a multifunctional methacrylate.
 44. Thecomposition of claim 33 wherein the UV initiator is a ketone.
 45. Aprocess for applying a seal to an article comprising the steps of A)blending at a temperature of between 25° C. and 250° C. 1) 70 to 99weight percent of a fluoroelastomer; 2) 0.5 to 20 weight percent of amultifunctional crosslinking agent selected from the group consisting ofmultifunctional acrylic crosslinking agents, multifunctional methacryliccrosslinking agents, multifunctional cyanurate crosslinking agents, andmultifunctional isocyanurate crosslinking agents; and 3) 0.1 to 10weight percent of a UV initiator  wherein the weight percentages of eachof components 1), 2), and 3) are based on the combined weight ofcomponents 1), 2), and 3); B) depositing said extrudable mixture on saidarticle in the shape and thickness desired to form an uncured seal; andC) irradiating said uncured seal with UV radiation for a time sufficientto cure said seal.
 46. The process of claim 45 wherein the curablecomposition is heated to a temperature of 90-170° C. in step A).
 47. Theprocess of claim 45 wherein the article is made of a thermoplasticmaterial.
 48. The process of claim 45 wherein the fluoroelastomer is acopolymer comprising copolymerized units of vinylidene fluoride.
 49. Theprocess of claim 45 wherein the fluoroelastomer is a copolymercomprising copolymerized units of tetrafluoroethylene.
 50. The processof claim 45 wherein the multifunctional crosslinking agent is amultifunctional acrylate.
 51. The process of claim 45 wherein themultifunctional crosslinking agent is a multifunctional methacrylate.52. A cured article produced by the process of claim
 45. 53. Thecomposition of claim 33 additionally comprising a foaming agent.
 54. Theprocess of claim 45 wherein the fluoroelastomer has a Mooney viscosityof 10-90 ML 1+4 (121° C.).
 55. A thermally stable, curable elastomercomposition consisting essentially of A) 80 to 97 weight percent of achlorinated elastomer selected from the group consisting of chlorinatedpolyolefin elastomers and epichlorohydrin elastomers; B) 2 to 19.5weight percent of a multifunctional crosslinking agent selected from thegroup consisting of multifunctional acrylic crosslinking agents,multifunctional methacrylic crosslinking agents, multifunctionalcyanurate crosslinking agents, and multifunctional isocyanuratecrosslinking agents; and C) 0.2 to 5.0 weight percent of a UV initiatorwherein the weight percentages of each of components A), B), and C) arebased on the combined weight of components A), B), and C).
 56. Thecomposition of claim 55 wherein the chlorinated elastomer is achlorinated polyolefin elastomer.
 57. The composition of claim 56wherein the chlorinated polyolefin elastomer is a chlorosulfonatedpolyolefin elastomer.
 58. The composition of claim 55 wherein thechlorinated elastomer is an epichlorohydrin elastomer.
 59. Thecomposition of claim 55 wherein the multifunctional crosslinking agentis a multifunctional acrylate.
 60. The composition of claim 55 whereinthe multifunctional crosslinking agent is a multifunctionalmethacrylate.
 61. The composition of claim 55 wherein the UV initiatoris a ketone.
 62. A process for applying a seal to an article comprisingthe steps of A) blending at a temperature of between 25° C. and 250°C. 1) 80 to 97 weight percent of a chlorinated elastomer selected fromthe group consisting of chlorinated polyolefin elastomers andepichlorohydrin elastomers; 2) 2 to 19.5 weight percent of amultifunctional crosslinking agent selected from the group consisting ofmultifunctional acrylic crosslinking agents, multifunctional methacryliccrosslinking agents, multifunctional cyanurate crosslinking agents, andmultifunctional isocyanurate crosslinking agents; and 3) 0.2 to 5.0weight percent of a UV initiator  wherein the weight percentages of eachof components 1), 2), and 3) are based on the combined weight ofcomponents 1), 2), and 3) to form a thermally stable, curable,exturdable mixture; B) depositing said extrudable mixture on saidarticle in the shape and thickness desired to form an uncured seal; andC) irradiating said uncured seal with UV radiation for a time sufficientto cure said seal.
 63. The process of claim 62 wherein the curablecomposition is heated to a temperature of 90-170° C. in step A).
 64. Theprocess of claim 62 wherein the article is made of a thermoplasticmaterial.
 65. The process of claim 62 wherein the chlorinated elastomeris a chlorinated polyolefin elastomer.
 66. The process of claim 62wherein the chlorinated polyolefin elastomer is a chlorosulfonatedpolyolefin elastomer.
 67. The process of claim 62 wherein thechlorinated elastomer is an epichlorohydrin elastomer.
 68. The processof claim 62 wherein the multifunctional crosslinking agent is amultifunctional acrylate.
 69. The process of claim 62 wherein themultifunctional crosslinking agent is a multifunctional methacrylate.70. The process of claim 62 wherein the UV initiator is a ketone.
 71. Acured article produced by the process of claim
 62. 72. The compositionof claim 55 additionally comprising a foaming agent.
 73. The process ofclaim 62 wherein the chlorinated elastomer has a Mooney viscosity of10-90, ML 1+4 (121° C.).
 74. A process for applying a seal to an articlecomprising the steps of A) blending at a temperature of between 25° C.and 250° C. 1) 80-98 weight percent of an ethylene alpha-olefincopolymer comprising ethylene and a C₃-C₂₀ alpha-olefin; 2) 1-19.5weight percent of a multifunctional crosslinking agent selected from thegroup consisting of multifunctional acrylic crosslinking agents andmultifunctional methacrylic crosslinking agents; and 3) 0.2-5 weightpercent of a UV initiator  wherein the weight percentages of each ofcomponents 1), 2), and 3) are based on the combined weight of components1), 2), and 3) to form a thermally stable, curable, extrudable mixture;B) depositing said extrudable mixture on said article in the shape andthickness desired to form an uncured seal; and C) irradiating saiduncured seal with UV radiation for a time sufficient to cure said seal.75. The process of claim 74 wherein the ethylene is an elastomericcopolymer of ethylene, a C₃-C₈ alpha-olefin and at least onenon-conjugated diene.
 76. A cured article produced by the process ofclaim 74.